Generalized policy server

ABSTRACT

A scalable access filter that is used together with others like it in a virtual private network to control access by users at clients in the network to information resources provided by servers in the network. Each access filter use a local copy of an access control database to determine whether an access request made by a user. Changes made by administrators in the local copies are propagated to all of the other local copies. Each user belongs to one or more user groups and each information resource belongs to one or more information sets. Access is permitted or denied according to of access policies which define access in terms of the user groups and information sets.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

The present application is a continuation and claims the prioritybenefit of U.S. patent application Ser. No. 12/850,587 filed Aug. 4,2010, which is a continuation and claims the priority benefit of U.S.patent application Ser. No. 11/897,626 filed Aug. 31, 2007, now U.S.Pat. No. 7,821,926, which is a continuation and claims the prioritybenefit of U.S. patent application Ser. No. 09/720,277 filed Mar. 12,2001, now U.S. Pat. No. 7,272,625, which is the U.S. National Phase andclaims the priority benefit of Application PCT/US99/14585 filed Jun. 28,1999; U.S. patent application Ser. No. 09/720,277 is also acontinuation-in-part and claims the priority benefit of U.S. patentapplication Ser. No. 09/034,507 filed Mar. 4, 1998, now U.S. Pat. No.6,408,336, which claims the priority benefit of U.S. ProvisionalApplication 60/039,542 filed Mar. 10, 1997 and U.S. ProvisionalApplication 60/040,262 filed Mar. 10, 1997; PCT applicationPCT/US99/14585 also claims the priority benefit of U.S. ProvisionalApplication 60/091,130 filed Jun. 29, 1998. The disclosures of theaforementioned applications are incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to control of access to data and relatesmore specifically to control of access to data in a distributedenvironment.

2. Description of Related Art

The Internet has revolutionized data communications. It has done so byproviding protocols and addressing schemes which make it possible forany computer system anywhere in the world to exchange information withany other computer system anywhere in the world, regardless of thecomputer system's physical hardware, the kind of physical network it isconnected to, or the kinds of physical networks that are used to sendthe information from the one computer system to the other computersystem. All that is required for the two computer systems to exchangeinformation is that each computer system have an Internet address andthe software necessary for the protocols and that there be a routebetween the two machines by way of some combination of the many physicalnetworks that may be used to carry messages constructed according to theprotocols.

The very ease with which computer systems may exchange information viathe Internet has, however, caused problems. On the one hand, it has madeaccessing information easier and cheaper than it ever was before; on theother hand, it has made it much harder to protect information. TheInternet has made it harder to protect information in two ways:

-   -   It is harder to restrict access. If information may be accessed        at all via the Internet, it is potentially accessible to anyone        with access to the Internet. Once there is Internet access to        information, blocking skilled intruders becomes a difficult        technical problem.    -   It is harder to maintain security en route through the Internet.        The Internet is implemented as a packet switching network. It is        impossible to predict what route a message will take through the        network. It is further impossible to ensure the security of all        of the switches, or to ensure that the portions of the message,        including those which specify its source or destination, have        not been read or altered en route.

FIG. 1 shows techniques presently used to increase security in networksthat are accessible via the Internet. FIG. 1 shows network 101, which ismade up of two separate internal networks 103 (A) and 103 (B) that areconnected by Internet 111. Networks 103 (A) and 103 (B) are notgenerally accessible, but are part of the Internet in the sense thatcomputer systems in these networks have Internet addresses and employInternet protocols to exchange information. Two such computer systemsappear in FIG. 1 as requestor 105 in network 103 (A) and server 113 innetwork 103 (b). Requestor 105 is requesting access to data which can beprovided by server 113. Attached to server 113 is a mass storage device115 that contains data 117 which is being requested by requestor 105. Ofcourse, for other data, server 113 may be the requestor and requestor105 the server. Moreover, access is to be understood in the presentcontext as any operation which can read or change data stored on server113 or which can change the state of server 113. In making the request,requestor 105 is using one of the standard TCP/IP protocols. As usedhere, a protocol is a description of a set of messages that can be usedto exchange information between computer systems.

The actual messages that are sent between computer systems that arecommunicating according to a protocol are collectively termed a session.During the session, Requestor 105 sends messages according to theprotocol to server 113's Internet address and server 113 sends messagesaccording to the protocol to requestor 105's Internet address. Both therequest and response will travel between internal network 103 (A) and103 (B) by Internet 111. If server 113 permits requestor 105 to accessthe data, some of the messages flowing from server 113 to requestor 105in the session will include the requested data 117. The softwarecomponents of server 113 which respond to the messages as required bythe protocol are termed a service.

If the owner of internal networks 103 (A and B) wants to be sure thatonly users of computer systems connected directly to networks 103 (A andB) can access data 117 and that the contents of the request and responseare not known outside those networks, the owner must solve two problems:making sure that server 113 does not respond to requests from computersystems other than those connected to the internal networks and makingsure that people with access to Internet 111 cannot access or modify therequest and response while they are in transit through Internet 111. Twotechniques which make it possible to achieve these goals are firewallsand tunneling using encryption.

Conceptually, a firewall is a barrier between an internal network andthe rest of Internet 111. Firewalls appear at 109 (A) and (B). Firewall109 (A) protects internal network 103 (A) and firewall 109 (B) protectsinternal network 103 (B). Firewalls are implemented by means of agateway running in a computer system that is installed at the pointwhere an internal network is connected to the Internet. Included in thegateway is an access filter: a set of software and hardware componentsin the computer system which checks all requests from outside theinternal network for information stored inside the internal network andonly sends a request on into the internal network if it is from a sourcethat has the right to access the information. Otherwise, it discards therequest. Two such access filters, access filter 107 (A), and accessfilter 107 (B), appear in FIG. 1.

A source has the right to access the requested information if twoquestions can be answered affirmatively:

-   -   Is the source in fact who or what it claims to be?    -   Does the source have the right to access the data?        The process of finding the answer to the first question is        termed authentication. A user authenticates himself or herself        to the firewall by providing information to the firewall that        identifies the user. Among such information is the following:    -   information provided by an authentication token (sometimes        called a smartcard) in the possession of the user;    -   the operating system identification for the user's machine; and    -   the IP address and the Internet domain name of the user's        machine.        The information that the firewall uses for authentication can        either be in band, that is, it is part of the protocol, or it        can be out of band, that is, it is provided by a separate        protocol.

As is clear from the above list of identification information, thedegree to which a firewall can trust identification information toauthenticate a user depends on the kind of identification information.For example, the IP address in a packet can be changed by anyone who canintercept the packet; consequently, the firewall can put little trust init and authentication by means of the IP address is said to have a verylow trust level. On the other hand, when the identification informationcomes from a token, the firewall can give the identification a muchhigher trust level, since the token would fail to identify the user onlyif it had come into someone else's possession. For a discussion onauthentication generally, see S. Bellovin and W. Cheswick, Firewalls andInternet Security, Addison Wesley, Reading, Mass., 1994.

In modern access filters, access is checked at two levels, the Internetpacket, or IP level, and the application level. Beginning with the IPlevel, the messages used in Internet protocols are carried in packetscalled datagrams. Each such packet has a header which containsinformation indicating the source and destination of the packet. Thesource and destination are each expressed in terms of IP address andport number. A port number is a number from 1 to 65535 used toindividuate multiple streams of traffic within a computer. Services forwell-known Internet protocols (such as HTTP or FTP) are assigned wellknown port numbers that they ‘listen’ to. The access filter has a set ofrules which indicate which destinations may receive IP packets fromwhich sources, and if the source and destination specified in the headerdo not conform to these rules, the packet is discarded. For example, therules may allow or disallow all access from one computer to another, orlimit access to a particular service (specified by the port number)based on the source of the IP packet. There is, however, no informationin the header of the IP packet about the individual piece of informationbeing accessed and the only information about the user is the sourceinformation. Access checking that involves either authentication of theuser beyond what is possible using the source information or determiningwhether the user has access to an individual piece of information thuscannot by done at the IP level, but must instead be done at the protocollevel.

Access checking at the application level is usually done in the firewallby proxies. A proxy is a software component of the access filter. Theproxy is so called because it serves as the protocol's stand-in in theaccess filter for the purposes of carrying out user authenticationand/or access checking on the piece of information that the user hasrequested. For example, a frequently-used TCP/IP protocol is thehyper-text transfer protocol, or HTTP, which is used to transferWorld-Wide Web pages from one computer to another such computer system.If access control for individual pages is needed, the contents of theprotocol must be inspected to determine which particular Web page isrequested. For a detailed discussion of firewalls, see the Bellovin andCheswick reference supra.

While properly-done access filtering can prevent unauthorized access viaInternet 111 to data stored in an internal network, it cannot preventunauthorized access to data that is in transit through Internet 111.That is prevented by means of tunneling using encryption. This kind oftunneling works as follows: when access filter 107 (A) receives an IPpacket from a computer system in internal network 103 (A) which has adestination address in internal network 103 (B), it encrypts the IPpacket, including its header, and adds a new header which specifies theIP address of access filter 107 (A) as the source address for the packetand the IP address of access filter 107 (B) as the destination address.The new header may also contain authentication information whichidentifies access filter 107 (A) as the source of the encrypted packetand information from which access filter 107 (B) can determine whetherthe encrypted packet has been tampered with.

Because the original IP packet has been encrypted, neither the headernor the contents of the original IP packet can be read while it ispassing through Internet 111, nor can the header or data of the originalIP packet be modified without detection. When access filter 107 (B)receives the IP packet, it uses any identification information todetermine whether the packet is really from access filter 107 (A). If itis, it removes the header added by access filter 107 (A) to the packet,determines whether the packet was tampered with and if it was not,decrypts the packet and performs IP-level access checking on theoriginal header. If the header passes, access filter 107 (B) forwardsthe packet to the IP address in the internal network specified in theoriginal header or to a proxy for protocol level access control. Theoriginal IP packet is said to tunnel through Internet 111. In FIG. 1,one such tunnel 112 is shown between access filter 107 (A) and 107 (B).An additional advantage of tunneling is that it hides the structure ofthe internal networks from those who have access to them only fromInternet 111, since the only unencrypted IP addresses are those of theaccess filters.

The owner of internal networks 103 (A) and 103 (B) can also usetunneling together with Internet 111 to make the two internal networks103 (A and B) into a single virtual private network (VPN) 119. By meansof tunnel 112, computer systems in network 103 (A) and 103 (B) cancommunicate with each other securely and refer to other computers as ifnetwork 103 (A) and 103 (B) were connected by a private physical linkinstead of by Internet 111. Indeed, virtual private network 119 may beextended to include any user who has access to Internet 111 and can dothe following:

-   -   encrypt Internet packets addressed to a computer system in an        internal network 103 in a fashion which permits an access filter        107 to decrypt them;    -   add a header to the encrypted packet which is addressed to        filter 107; and    -   authenticate him or herself to access filter 107.        For example, an employee who has a portable computer that is        connected to Internet 111 and has the necessary encryption and        authentication capabilities can use the virtual private network        to securely retrieve data from a computer system in one of the        internal networks.

Once internal networks begin using Internet addressing and Internetprotocols and are connected into virtual private networks, the browsersthat have been developed for the Internet can be used as well in theinternal networks 103, and from the point of view of the user, there isno difference between accessing data in Internet 111 and accessing it ininternal network 103. Internal network 103 has thus become an intranet,that is, an internal network that has the same user interface asInternet 111. Of course, once all of the internal networks belonging toan entity have been combined into a single virtual private intranet, theaccess control issues characteristic of the Internet arise again—exceptthis time with regard to internal access to data. While firewalls at thepoints where the internal networks are connected to Internet 111 areperfectly sufficient to keep outsiders from accessing data in theinternal networks, they cannot keep insiders from accessing that data.For example, it may be just as important to a company to protect itspersonnel data from its employees as to protect it from outsiders. Atthe same time, the company may want to make its World Wide Web site on acomputer system in one of the internal networks 103 easily accessible toanyone who has access to Internet 111.

One solution to the security problems posed by virtual private intrantsis to use firewalls to subdivide the internal networks, as well as toprotect the internal networks from unauthorized access via the Internet.Present-day access filters 107 are designed for protecting the perimeterof an internal network from unauthorized access, and there is typicallyonly one access filter 107 per Internet connection. If access filtersare to be used within the internal networks, there will be many more ofthem, and virtual private networks that use multiple present-day accessfilters 107 are not easily scalable, that is, in virtual privatenetworks with small numbers of access filters, the access filters arenot a serious burden; in networks with large numbers of access filters,they are. The access filters described in the part of the present patentapplication which precedes the section titled Generalization of thetechniques employed in access filter 203 in fact solves the scalabilityproblems of prior-art access filters and thus greatly ease theimplementation of networks with large numbers of access filters.

In the course of further work on the access filters described in thefirst part of the present patent application, it has become apparentthat the techniques developed to do access checking in access filter 203would be even more useful if they could be generalized: if they could beused in contexts other than access filters operating at the IP filter orInternet protocol levels and if they could be made to be extensible, sothat policies could be made not only for access to information sets, butfor any action that could be performed on an entity accessible through acomputer system, so that user groups could include any kind of entitythat can perform an action through a computer system, and so thatinformation sets could become resource sets, where a resource is anyentity that can be controlled via a computer system. It further becameapparent that policies would be even more useful if they were permittedto include a temporal component, for example, a component whichpermitted a certain group of users access to certain resources onlyduring non-working hours and that it would also be beneficial to be ableto associate attributes with a policy that described how the policy'saction was to be performed. For instance, a policy might specify notonly that members of a given user group could access a given resource,but also the class of network service to be used for the access. It isthus an object of the invention disclosed herein to provide techniquesfor generalized access checking and to further provide policies in whichtemporal components and attributes may be associated with policies.

SUMMARY OF THE INVENTION

The invention attains the foregoing object by means of a policyenforcement system in which the task of policy enforcement is sharedbetween two components: a policy server that includes an extensiblepolicy database and a policy enforcer. When the policy enforcer receivesa request by a first entity to perform an action on a second entity, thepolicy enforcer communicates the request to the policy server andpermits the action only if a response from the policy server indicatesthat the policies in the database allow the action. The extensiblepolicy database may be extended to include actions of types notperformed by the policy enforcer. Because this is so, the policyenforcement system can deal with new types of actions by extending thepolicy database to provide policies for those types and adding policyenforcers for actions of the types. Indeed, as long as an action iscontrolled by a policy enforcer in the computer system, there is norequirement that the computer system perform the action.

Separation of policy evaluation from policy enforcement also makes itpossible for the policy enforcement system to easily handle policyenforcement at different levels of the computer system to which thepolicy enforcement system belongs and for the policy enforcers to belocated remotely from the policy server.

In another aspect, policies are defined in one embodiment of the policyenforcement system in terms of a set of first entities, a set of secondentities, and an action which an entity of the first set may perform onan entity of the second set. In this embodiment, the types of firstentities and the types of second entities are extensible in addition tothe types of actions.

In this embodiment, action attributes that determine how the actionwhich is the subject of the policy is to be performed may be attached tothe sets of first entities or the sets of second entities. For example,a priority may be assigned to a set of users or a bandwidth to a set ofservices. The policy database of the embodiment is extensible to includenew types of action attributes.

In another aspect of the invention, conditions may be attached topolicies in the policy database of the policy enforcement system. Evenwhen a policy's action would otherwise be permitted, it will not bepermitted if the condition attached to the policy is not fulfilled. Oneclass of such conditions is temporal conditions. For instance, a policymay be made which defines access to information and a temporal conditionon the policy may restrict the policy's validity to normal businesshours.

Other objects and advantages of the invention will be apparent to thoseskilled in the arts to which the invention pertains upon perusing thefollowing Detailed Description and Drawing, wherein:

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an overview of techniques used to control access ofinformation via the Internet;

FIG. 2 is an overview of a VPN that uses access filters incorporatingthe techniques disclosed herein;

FIG. 3 is an overview of an access control database that is used in theaccess filters;

FIG. 4 shows access checking and tunneling in a VPN that uses accessfilters incorporating the techniques disclosed herein;

FIG. 5 shows access by a “roamer” to information in the VPN;

FIG. 6 is a table used in defining the relationship between sensitivityand trust levels and authentication and encryption techniques;

FIG. 7 is an example of the application of SEND;

FIG. 8 is a flow chart of the policy creation process;

FIG. 9 shows a display used to define user groups;

FIG. 10 shows a display used to define information sets;

FIG. 11 shows a display used to define access policies;

FIG. 12 shows a display used to define an access filter 203;

FIG. 13 is a schema of the part of access control database 301 thatdefines user groups;

FIG. 14 is a schema of the part of access control database 301 thatdefines information sets;

FIG. 15 is a schema of the part of access control database 301 thatdefines sites in the VPN and the servers, services, and resources ateach site;

FIG. 16 is a schema of the part of access control database 301 thatdefines policies;

FIG. 17 is a schema of the part of access control database 301 thatdefines servers;

FIG. 18 shows the display used in the IntraMap interface;

FIG. 19 shows how changes are made to access control database 301;

FIG. 20 is a detailed block diagram of the architecture of an accessfilter 203;

FIG. 21 is a diagram of the structure of an MMF file 2303;

FIG. 22 is a diagram of a message sent using SKIP;

FIGS. 23A, B, and C are a table of the MMF files employed in a preferredembodiment;

FIG. 24 is a diagram of an implementation of the IntraMap interface;

FIG. 25 is a diagram illustrating delegation in VPN 201;

FIG. 26 is a block diagram of an action control system where policychecking has been separated from policy enforcement;

FIG. 27 is a block diagram of an action control system with a variety ofpolicy-enabled devices;

FIG. 28 shows a syntax used to define generalized policies;

FIG. 29 shows an overview of policy database 2901 in a preferredembodiment;

FIG. 30 shows an implementation of attributes and time intervals inpolicy database 2901;

FIG. 31 shows a window that lists all defined schedules;

FIG. 32 shows a window used in a preferred embodiment to define aschedule rule;

FIG. 33 shows a window used in a preferred embodiment to apply aninterval of time to a policy;

FIG. 34 shows a window used in a preferred embodiment to displayattributes;

FIG. 35 shows a window used in a preferred embodiment to assignattributes to subjects;

FIG. 36 shows a window that is used to display and modify the definitionof an attribute in a preferred embodiment; and

FIG. 37 shows a window that is used to display and modify the definitionof a feature in a preferred embodiment.

The reference numbers in the drawings have at least three digits. Thetwo rightmost digits are reference numbers within a figure; the digitsto the left of those digits are the number of the figure in which theitem identified by the reference number first appears.

For example, an item with reference number 203 first appears in FIG. 2.

DETAILED DESCRIPTION

The following Detailed Description will first provide an overview ofaccess filters that are easily scalable, of how they are used to controlaccess in intrants, and of how they can be used to construct virtualprivate networks. Thereupon, the Detailed Description will providedetails of the access control database used in the filters, of themanner in which it is changed and those changes are distributed amongthe filters, and of the manner in which an individual filter controlsaccess.

A Network with Access Filters that do not Interfere with Scalability:FIG. 2.

FIG. 2 shows a virtual private network (VPN) 201 in which access to datais controlled by access filters that are designed to avoid the problemsposed by multiple access filters. VPN 201 is made up of four internalnetworks 103 which are connected to each other by Internet 121. Alsoconnected to VPN 201 via Internet 121 is a roamer 217, that is, acomputer system which is being used by a person who may access data inintranet 201, but is connected to the internal networks only by Internet121. Each internal network 103 has a number of computer systems orterminals 209 belonging to users and a number of servers 211 whichcontain data that may be accessed by users at systems or terminals 209or by a user at roamer 217. However, no computer system or terminal 209or roamer 217 is connected directly to a server 211; instead, each isconnected via an access filter 203, so that all references made by auser at a user system to a data item on a server go through at least oneaccess filter 203. Thus, user system 209 (i) is connected to network 213(i), which is connected to access filter 203 (a), while server 211 (i)is connected to network 215 (i), which is also connected to accessfilter 203 (a), and any attempt by a user at user system 209 (i) toaccess data on server 211 (i) goes through access filter 203 (a), whereit is rejected if the user does not have the right to access the data.If VPN 201 is of any size at all, there will be a substantial number ofaccess filters 203, and consequently, scaling problems will immediatelyarise. Access filters 203 avoid these problems because they are designedaccording to the following principles:

-   -   Distributed access control database. Each access filter 203 has        its own copy of the access control database used to control        access to data in VPN 201. Changes made in one copy of the        database are propagated to all other copies.    -   Distributed administration. Any number of administrators may be        delegated responsibility for subsets of the system. All        administrators may perform their tasks simultaneously.    -   Distributed access control. Access control functions are        performed at the near-end access filter 203. That is, the first        access filter 203 in the path between a client and the server        determines if the access is allowed and subsequent access        filters in the path do not repeat the access checks made by the        first access filter.    -   End-to-end encryption. Encryption occurs between the near-end        access filter and the furthest encryption endpoint possible.        This endpoint is either the information server itself or the        far-end access filter 203—the one last in the route from client        to server. Dynamic tunnels are created based on current network        routing conditions.    -   Adaptive encryption and authentication. Variable levels of        encryption and authentication requirements are applied to        traffic passed through the VPN, based on the sensitivity of the        information being transmitted.

All of these aspects of the design will be discussed in more detailbelow.

It should be pointed out at this point that access filter 203 may beimplemented in any fashion which ensures that all references to data inVPN 201 which are made by users who may not be authorized to access thatdata go through an access filter 203. In a preferred embodiment, accessfilter 203 is implemented on a server and runs under the Windows NToperating system manufactured by Microsoft Corporation. In otherembodiments, access filter 203 may be implemented as a component of anoperating system and/or may be implemented in a router in VPN 201.

Distributed Policy Database: FIG. 3

Each access filter 203 has a copy of an access control database 301 thatholds all data relevant to access control in VPN 201. One access filter,shown as access filter 203 (a) in FIG. 2, has a master copy 205 ofaccess control database 301. Because of this, access filter 203 (a) istermed the Master Policy Manager. The master copy 205 is the one that isused to initialize new access filters 203 or replace a damaged accesscontrol database 301. The backup for the master policy manager computeris access filter 203 (b). Backup 207 is a minor image of master copy205. Report manager 209, finally, includes software for generatingreports from the information in access control database 301 and fromlogs obtained from all other access filters 203. Any copy of accesscontrol database 301 may be altered by any user who has the accessrequired to do so; as will be described in more detail later, any suchalteration is propagated first to master policy manager 205 and then toall of the other access filters 203 in virtual private network 201.

FIG. 3 is a conceptual overview of access control database 301. Theprimary function of the database is to respond to an access request 309from access filter 203 which identifies a user and an informationresource with an indication 311 of whether the request will be grantedor denied. The request will be granted if both of the following aretrue:

-   -   The user belongs to a user group which data base 301 indicates        may access an information set to which the information resource        belongs; and    -   the request has a trust level which is at least as high as a        sensitivity level belonging to the information resource.

Each user belongs to one or more of the user groups and each informationresource belongs to one or more information sets; if none of the usergroups that the user belongs to is denied access to an information setthat the resource belongs to and any of the user groups that the userbelongs to is allowed access to any of the information sets that theinformation resource belongs to, the user may access the informationresource, provided that the request has the requisite trust level.

The sensitivity level of a resource is simply a value that indicates thetrust level required to access the resource. In general, the greater theneed to protect the information resource, the higher its sensitivitylevel. The trust level of a request has a number of components:

-   -   the trust level of the identification technique used to identify        the user; for example, identification of a user by a token has a        higher trust level than identification of the user by IP        address.    -   the trust level of the path taken by the access request through        the network; for example, a path that includes the Internet has        a lower trust level than one that includes only internal        networks.    -   if the access request is encrypted, the trust level of the        encryption technique used; the stronger the encryption        technique, the higher the trust level.

The trust level of the identification technique and the trust level ofthe path are each considered separately. The trust level of the pathmay, however, be affected by the trust level of the encryption techniqueused to encrypt the access request. If the request is encrypted with anencryption technique whose trust level is higher that the trust level ofa portion of the path, the trust level of the portion is increased tothe trust level of the encryption technique. Thus, if the trust level ofa portion of a path is less than required for the sensitivity level ofthe resource, the problem can be solved by encrypting the access requestwith an encryption technique that has the necessary trust level.

The information contained in database 301 may be divided into five broadcategories:

-   -   user identification information 313, which identifies the user;    -   user groups 315, which defines the groups the users belong to;    -   information resources 320, which defines the individual        information items subject to protection and specifies where to        find them;    -   information sets 321, which defines groups of information        resources;    -   trust information 323, which specifies the sensitivity levels of        information resources and the trust levels of user        identifications and network paths; and policy information 303,        which defines access rights in terms of user groups and objects        in VPN 201.

Policy information is further divided into access policy 307,administrative policy 305, and policy maker policy 306.

-   -   access policy 307 defines rights of access by user groups to        information sets;    -   administrative policy 305 defines rights of user groups to        define/delete/modify objects in VPN 201. Among the objects are        access policies, information sets, user groups, locations in VPN        201, servers, and services; and    -   policy maker policy 306 defines rights of user groups to make        access policy for information sets.

The user groups specified in the administrative policy and policy makerpolicy portions of database 301 are user groups of administrators. InVPN 201, administrative authority is delegated by defining groups ofadministrators and the objects over which they have control in database301. Of course, a given user may be a member of both ordinary usergroups 317 and administrative user groups 319.

Identification of Users

User groups identify their members with user identification information313. The identification information identifies its users by means of aset of extensible identification techniques. Presently, theseidentification techniques include X.509 certificates, Windows NT Domainidentification, authentication tokens, and IP address/domain name. Thekind of identification technique used to identify a user determines thetrust level of the identification.

Where strong identification of a user or other entity that an accessfilter 203 communicates with is required, VPN 201 employs the Simple KeyManagement for Internet Protocols (SKIP) software protocol, developed bySun Microsystems, Inc. The protocol manages public key exchange,authentication of keys, and encryption of sessions. It does sessionencryption by means of a transport key generated from the public andprivate keys of the parties who are exchanging data. Public keys areincluded in X.509 certificates that are exchanged between SKIP partiesusing a separate protocol known as the Certificate Discovery Protocol(CDP). A message that is encrypted using SKIP includes in addition tothe encrypted message an encrypted transport key for the message andidentifiers for the certificates for the source and destination of thedata. The recipient of the message uses the identifiers for thecertificate of the source of the message to locate the public key forthe source, and uses its keys and the source's public key to decrypt thetransport key and uses the transport key to decrypt the message. A SKIPmessage is self-authenticating in the sense that it contains anauthentication header which includes a cryptographic digest of thepacket contents and modification of any kind will render the digestincorrect.

In VPN 201, SKIP is also used by access filters 203 to identifythemselves to other access filters 203 in the VPN and to encrypt TCP/IPsessions where that is required. Access filters 203 can also use thecertificates for the SKIP keys to identify users when they areperforming access checks. Such an identification is particularlytrustworthy and has a correspondingly high trust level. One use for suchidentification by mean of certificate is for trustworthy identificationof a “roamer” 217. The X.509 certificates can be used for useridentification because they relate the key information to informationabout the user.

Access filter 203 uses the following fields of information from thecertificates:

-   -   Expiration Date. The date after which the certificate is        invalid.    -   Public Key. The public half of a public-private key pair, as        used in the SKIP-based cryptography that Conclave uses.    -   Certificate Authority Signature. The distinguished name        associated with the authority that issued the certificate.    -   Serial Number for the certificate    -   Subject name, the name of the entity the certificate was issued        to. The subject name includes the following subfields (the value        in parentheses is the common abbreviation for the field):        -   Common Name (CN). The given name of the subject, for            example, John Q. Public.        -   Country (C). The country in which the subject resides.            Country codes are 2-letter codes specified in the X.509            specification.        -   Locality (L). The location at which the subject resides.            This is usually the city in which the subject resides, but            can be used for any location-related value.        -   Organization (O). The organization to which the subject            belongs. This is usually the organization's name.        -   Organizational Unit (OU). The organizational unit for the            subject. This is usually the department for the subject, for            example, “sales”. The X.509 certificate allows up to four of            these fields to exist.

A Certificate Authority used with access filters 203 issues certificateswith all of these fields. Further, the four OU fields can be used todefine additional categories. The information used to describe a user ina certificate is available to the administrators of data base 301 foruse when defining user groups. If the information in the certificatesproperly reflects the organizational structure of the enterprise, acertificate will not only identify the user, but show where the userfits in the enterprise's organization and to the extent that the usergroups in data base 301 reflect the organizational structure, the usergroups that the user belongs to.

As will be explained in more detail later, one way in which members ofuser groups may be defined is by certificate matching criteria whichdefine the values of the fields which a certificate that belongs to amember of a given user group must have. The certificate matchingcriteria can be based on as few or as many of the above fields asdesired. For example, the certificate matching criteria for theEngineering user group might be the organization field and anorganization unit field specifying the engineering department. Otherinformation that identifies a user may be used to define members of usergroups as well.

Information Sets

Information sets hold collections of individual information resources. Aresource may be as small as an individual WWW page or newsgroup, butmost often it will consist of a Web directory tree and its contents, FTPaccounts, or major Usenet news categories.

Two information sets, 219 (j) and (k), are shown in one of the serversof FIG. 2. While it is completely up to the administrators of accesscontrol database 301 to determine what information is included in aninformation set, the information in a given set will generally beinformation that is related both topically and by intended audience.Example information sets for a corporation might be HR policies, HRPersonnel Records, and Public Information.

Access Policy 307

Conceptually, access policy 307 consists of simple statements of theform:

-   -   Engineers allowed access to engineering data    -   Internet allowed access to public web site        The first column specifies user groups; the last column        specifies information sets. The middle column is the access        policy-allow or deny.

Database 301 permits hierarchical definition of both user groups andinformation sets. For example, the Engineers user group may be definedas including a Hardware Engineers user group, a Software Engineers usergroup, and a Sales Engineers user group. Similarly, the engineering datainformation set may be defined as including a hardware engineering datainformation set, a software engineering data information set, and asales engineering data information set. Access rights are inheritedwithin hierarchies of user groups.

Thus, a user who belongs to the Hardware Engineers user group alsoautomatically belongs to the Engineers user group for access checkingpurposes. Access rights are similarly inherited within hierarchies ofinformation sets. An information resource that belongs to the hardwareengineering information set also automatically belongs to theengineering data information set for access checking purposes. Thus, ifthere is an access policy that gives Engineers access to engineeringdata, any user who is a member of one of the three user groups making upEngineers may access any information resource that belongs to any of thethree information sets making up engineering data. The use ofinheritance in the definitions of user groups and information setsgreatly reduces the number of access policies 307 that are required inaccess control database 301. For instance, in the above example, asingle access policy gives all engineers access to all engineering data.Inheritance also makes it possible to define virtually all accesspolicies in terms of allowing access. Continuing with the above example,if there is a user group Salespeople that does not belong to Engineersand there is an access policy that gives that user group access to salesengineering data, a user who is a member of Salespeople will be able toaccess sales engineering data, but not software engineering data orhardware engineering data.

A user may of course belong to more than one user group and aninformation resource may belong to more than one information set. Theremay also be different access policies for the various user groups theuser belongs to and the various information sets the informationresource belongs to. When faced with multiple access policies that applyto the user and to the information resource that the user is seeking toaccess, access filter 203 applies the policies in a restrictive, ratherthan permissive way:

-   -   If multiple policies allow or deny a user group's access to an        information set, policies that deny access prevail.    -   If a particular user is a member of multiple user groups, and        multiple policies allow or deny access to the information set,        policies that deny access prevail.

What user groups a user belongs to may vary according to the mode ofidentification used to identify the user. Thus, if no access policiesapply for the user groups that the user belongs to according to themodes of identification that the user has thus far provided to accessfilter 203, access filter 203 may try to obtain additionalidentification information and determine whether the additionalidentification information places the user in a user group for whichthere is a policy regarding the resource. Access filter 203 may obtainthe additional identification information if:

-   -   The user has installed the User Identification Client (software        that runs on the user's machine and provides identification        information about the user to access filter 203).    -   The UIC is currently running on the user's machine.    -   The user has enabled his UIC to pop-up for further        authentication. (The user has a check box that enables this        feature.)

If all of these requirements are true, then access filter 203 will forcethe user's UIC to pop-up and ask for further identification information.Any identification information that the user supplies is saved. Aftereach new piece of user identification information, access filter 203performs the same evaluation process, popping up the UIC window untilidentification information is obtained that places the user in a usergroup for which there is an access policy that permits or denies accessor until the user gives up on his or her request.

Administrative Policies 305

The administrative policies 305 implement administration of objects inVPN 201's access control system. Included in the objects are usergroups, information sets, access policies, and what are termed hereinavailable resources, that is, the services, servers, access filters, andnetwork hardware making up VPN 201. An object is administered by one ormore administrative user groups. A member of an administrative usergroup that administers a given object may modify the object and itsrelationship to other objects and may make administrative policy for theobject. As will be explained in more detail later, the fact that amember of an administrative user group that administers an object maymake administrative policy for the object makes it possible for themember to delegate administration of the object. For example, a memberof an administrative user group that administers a Hardware Engineersuser group may make an administrative policy that gives administrationof the Hardware Engineers to a Hardware Engineering Administrator usergroup, thereby delegating administration of Hardware Engineers toHardware Engineering Administrator. It should be noted that the right toadminister an information set is separate from the right to make accesspolicy for the information set. The fact that a user group has the rightto make access policy concerning an information set does not give theuser group the right to make administrative policy for the informationset, and vice-versa. When an access filter 203 is first set up, a singlebuilt-in security officer user group has administrative authority overall of the objects in VPN 201 and over policy maker policy 306.

Inheritance with Administrative Policy

Inheritance works with administrative policy the same way that it doeswith access policy.

The user groups, information sets, and available resources to whichadministrative policies are directed are hierarchically organized:Within the user groups, user groups that are subsets of a given usergroup are at the next level down in the hierarchy of user groups fromthe given user group. The same is the case with information sets.Inheritance applies within the hierarchy in the same fashion as withaccess policy. Thus, within the user group hierarchy an administrativeuser who controls a user group also controls all subsidiary, containeduser groups. Similarly, with the information set hierarchy anadministrative user who controls the information set also controls allsubsidiary, contained information sets and an administrative user whocontrols access policy for an information set also controls accesspolicy for all contained information sets.

There is further a natural hierarchy of available resources. Forexample, one level of the hierarchy is locations. Within a givenlocation, the servers at that location form the next level down, andwithin a server, the services offered by the service form the nextlevel.

The administrative user group that has control of any level of theavailable resources tree also controls all lower levels. For example,the administrator (s) to whom an administrative policy gives control ofan access filter 203 has administrative rights to all servers beneaththat site, all services running on those servers and all resourcessupported by those services.

Delegation: FIG. 25

Delegation is easy in VPN 201 because the members of the administrativeuser group that administers an object may both modify the object andmake administrative policy for it. For example, if an administrativeuser group administers an information set, it can divide the informationset into two subsets and make new administrative policies which giveeach of two other user groups administrative authority over one of thetwo subsets.

FIG. 25 gives an extended example of delegation. In FIG. 25, user groupsand other objects are represented by circles; policy maker policy isrepresented by a square box; policy relationships are expressed bydifferent kinds of arrows: a solid arrow for administrative policy, adotted arrow for policy maker policy, and a dashed arrow for accesspolicy. The part of the figure labeled 2501 shows the situation whenaccess filter 203 is being set up: the built-in Security Officer usergroup 2503 has administrative authority over all of the built-in objects2505 and over policy maker policy 2507. Members of Security Officer usergroup 2503 use their administrative authority to make subsets of objects2505, rearrange the object hierarchies, and set up policy maker policy2507.

One result of the activity of Security Officer user group 2503'sactivity is seen in the section of FIG. 25 labeled 2508. A member ofSecurity Officer user group 2503 has set up an EngineeringAdministrators administrative user group 2509, an Engineers user group2511, and an Engineering Data information set 2513 and has givenEngineering Administrators administrative authority over Engineers andEngineering Data. The member of Security Officer has also set up policymaker policy 2507 so that Engineering Administrators has the right tomake access policy for Engineering Data, as shown by dotted arrow 2510.A member of Engineering Administrators has used that right to makeaccess policy that permits members of Engineers 2511 to accessinformation in Engineering Data 2513, as shown by dashed arrow 2512. Themember of Security Officer has thus delegated the administrativeauthority over Engineers 2511, Engineering Data 2513, and over access toEngineering Data to Engineering Administrators 2509.

Security Officer 2503 of course still has administrative authority overEngineering Administrators and can use that authority for furtherdelegation. An example is shown at 2517. A member of Security Officer2503 has divided Engineering Administrators into two subsets:Engineering Personnel Administrators (EPA) 2519 and Engineering DataAdministrators (EDA) 2521. The members of these subsets inheritadministrative rights over Engineers 2511 and Engineering Data 2513 fromEngineering Administrators 2509. The members of EPA 2519 and EDA 2521use these administrative rights to delegate administrative authorityover Engineers 2511 to Engineering Personnel Administrators 2519 andadministrative authority over Engineering Data 2513 to Engineering DataAdministrators 2521. The members of EPA 2519 and EDA 2521 have furtherused their right to make access policy for Engineering Data 2513 tochange the access policy so that access policy for Engineering Data ismade by Engineering Data Administrators 2513, as shown by dotted arrow2523, instead of by Engineering Administrators, thereby delegating thatfunction to Engineering Data Administrators.

Members of Engineering Personnel Administrators and Engineering DataAdministrators can now use their administrative rights over Engineers,Engineering Data, and access policy for Engineering Data to refineaccess to Engineering Data. For example, a member of EngineeringPersonnel Administrators might subdivide Engineers into SoftwareEngineers and Hardware Engineers and a member of Engineering DataAdministrators might subdivide Engineering Data into HardwareEngineering Data and Software Engineering Data.

That done, a member of Engineering Data Administrators might replace theaccess policy giving Engineers access to Engineering Data with accesspolicies that give Software Engineers access to Software EngineeringData and Hardware Engineers access to Hardware Engineering Data.

In summary, it may be said that the administrators who have control overa user group are responsible for correctly defining membership in theuser group; they may delegate any part of this responsibility to otheradministrators. Similarly, administrators who have control over aninformation set are responsible for correctly including informationresources into the information set; they may delegate any part of thisresponsibility to other administrators. The latter administrators mustof course also be administrators for some available resource from whichthe information being added to the information set may be obtained.Administrators of available resources carry responsibility for overallnetwork and security operation. Likewise, they may delegate theirresponsibilities. Policy maker administrators, finally, hold theultimate control over access to information. They alone may createaccess policies related to specific information sets. In a sense, thepolicy makers determine the overall information sharing policy for theenterprise. Administrators for the user groups, information sets, andavailable resources then determine the particulars of implementation.

Access Control Using Filters 203 and Database 301: FIG. 4

As shown in FIG. 2, an access filter 203 has a position in VPN 201 whichputs it between the client from which the user is requesting access tothe information resource and the server upon which the informationresource resides. The access filter 203 is thus able to control accessby the user to the resource by interceding in the communication betweena user and a service on the server which is able to provide the userwith access to the information resource. In order for the user to gainaccess to the information resource, a session must be establishedbetween the user and the service. In the present context, the termsession is defined liberally, to include well-behaved connectionlessprotocols. When an access filter 203 observes an attempt by a user toinitiate a session with a service, it determines whether access shouldbe permitted. It does so from the known identity of the user, theinformation resource to which the information is being accessed, thesensitivity level of the information, and the trust levels of the useridentification, of the path between the user and the service, and of anyencryption technique used.

FIG. 4 shows how a session can involve more than one access filter 203.Session 402 shown in FIG. 4 involves five access filters 203, numbered403 (1 . . . 5) in the Figure. Access filters 203 are designed such thatthe decision whether to grant a user access to an information resourceneed only be made in one of the access filters 203. The key to thisfeature of access filters 203 is their ability to authenticatethemselves to each other. SKIP is used to do this. Every access filter203 has an X.509 certificate that binds the access filter 203's keys tothe access filter's name and is signed by the Certificate Authority forthe VPN. Each access filter 203 has the names and IP addresses of all ofthe other access filters in VPN 201 in data base 301, and upon arrivalof a session that is encrypted using SKIP, each access filter uses theSubject Name from the certificates as described above in the discussionof SKIP to determine whether SKIP-encrypted network traffic is fromanother access filter 203 in VPN 201.

If the access filter receiving the session is not the destination of thesession, (that is, the access filter functions simply as an IP routeralong the path), the access filter merely verifies from data base 301that the destination IP address is the IP address of some other accessfilter 203 in VPN 201. If that is the case, then the session is allowedto pass without additional checking. When the request reaches the lastaccess filter 203, the last access filter 203 uses SKIP to decrypt therequest, to confirm that the request was indeed checked by the firstaccess filter 203, and to confirm that the request has not been modifiedin transit.

Thus, in FIG. 4, access filter 403 (1) uses its own copy of accesscontrol database 301 to determine whether the user who originates asession has access to the information resource specified for thesession. If access filter 403 (1) so determines, it authenticates thesession's outgoing messages and encrypts them as required to achieve theproper trust level. Access filters 403 (2 . . . 5) then permit thesession to proceed because the session is from access filter 403 (1) andhas been encrypted with SKIP and neither decrypt the messages nor checkthem using their own copies of access control database 301. Accessfilter 403 (5) then decrypts the messages, confirms that they wereencrypted and therefore checked by access filter 403 (1), and if themessages are intact, forwards them to server 407 that contains thedesired resource. Messages in the session which pass between server 407and user system 401 are treated in the same way, with access filter 403(5) encrypting them if necessary, access filters 403 (2 . . . 4) passingthem through on the basis of the authentication by 403 (5), and accessfilter 403 (1) passing the message on to system 401 on the basis of theauthentication and decrypting the message if necessary.

What this technique effectively does is to make a tunnel 405 for thesession between access filter 403 (1) and access filter 403 (5), andbecause of the tunnel, only the access filter 403 closest to the clientneeds to do decryption, access checking, and reencryption. Moreover, thetunnel is equally secure in the internal networks and in Internet 121.In a large VPN, access filter 403 (1) is in the best position to checkaccess, because it has access to the most detailed information about theuser who originates the session. The technique of performing the accesscheck at the first access filter 401 further distributes the accesscontrol responsibility evenly across the VPN, allowing it to scale toany size.

End-to-End Encryption: FIG. 5

Tunnel 405 of FIG. 4 extends only from access filter 403 (1) to accessfilter 403 (5); the messages of the session are unencrypted betweensystem 401 employed by the user and access filter 403 (1) and againbetween access filter 403 (5) and server 407 that contains theinformation resource. In the case of extremely sensitive information,authentication and encryption may be needed from the near end accessfilter to the end of the path through the network, namely between system403 (1) and server 407.

FIG. 5 shows how this is accomplished using access filters 203. Withinthe VPN, authentication and encryption may be used with any clientsystem 401 or 503 or any server system 407 in addition to access filters203. When a client computer utilizes encryption, it uses SKIP toauthenticate the session and encrypt it using a shared secret that isshared between the client computer and a selected access filter 203 andthen sends the encrypted message to the selected access filter 203,thereby effectively establishing a tunnel between the client and theselected access filter 203 and making the selected access filter 203 thefirst access filter 203 for purposes of access checking. At the firstaccess filter 203, the messages are decrypted and access checking isdone. Since SKIP makes available the user's certificate along with theencrypted message, the user's authenticated identity can be used foraccess checking. If the access is permitted, the message is once againencrypted and sent to access filter 403 (5) nearest server 407, whichdecrypts it. If data base 301 contains a SKIP name and encryptionalgorithms for server 407, access filter 403 (5) retrieves thecertificate for server 407 if necessary and uses SKIP to reencrypt thesession as required for server 407. Otherwise, access filter 403 (5)simply sends the message to server 407 in the clear. If the message wasreencrypted for server 407, server 407, finally, receives the encryptedmessage and decrypts it. The access filters 203 intermediate to thefirst access filter 203 and last access filter 203 simply note that themessage is from another access filter and is encrypted with SKIP andpass the message on, as described above. When server 407 retrieves theinformation resource, it either sends it in the clear to access filter403 (5) or encrypts the message containing the resource with the key foraccess filter 403 (5). The process of decrypting and encryptingdescribed above is then performed in reverse, pairwise, from server 407to access filter 403 (5), from access filter 403 (5) to access filter403 (1), and finally from access filter 403 (1) to the original clientsystem, which decrypts it.

The effect of this technique is to construct a tunnel on the pathbetween the client and the server which runs from the access filter 203on the path which is nearest to the client to the access filter 203 onthe path which is nearest to the server. If the client is capable ofencryption and decryption, the tunnel can be extended from the accessfilter nearest the client to the client and if the server is capable ofencryption and decryption, the tunnel can be similarly extended to fromthe access filter nearest the server to the server. Once the firstaccess filter 203 in the path has been reached and has authenticated thesession, no further encryption or decryption is required until theaccess filter 203 nearest the server has been reached. Moreover, accesscontrol database 301 in each access filter 203 contains all of thenecessary identification and certification information for the client,the server, and the access filters 203 in the route. An advantage of theend-to-end encryption technique just described is that it distributesencryption load throughout the network, rather than concentrating it atthe access filters connecting the VPN to the Internet, and therebyenhances scalability.

FIG. 5 shows how the technique works with a session 501 that originateswith a roamer, that is, a client 503 whose connection to the VPN is viaInternet 121. Roamer 503 is equipped with SKIP, as is target server 407on an internal network. When SKIP was configured in the roamer, it wasgiven the certificate for access filter 403 (3) and access filter 403(3) was given the certificate for the roamer. When roamer 503 sends amessage belonging to the session, it addresses the message to server 407and encrypts it using a transport key which it shares with access filter403 (3). The message is thus tunneled via tunnel 505 to access filter403 (3). There, access filter 403 (3) decrypts the session, performs theaccess check, and reencrypts it using a transport key for access filter403 (5).

The subsequent access filters 403 in the path allow the session throughbecause it is authenticated by access filter 403 (3), thus providingtunnel 507 to at least access filter 403 (5). If target server 407 isSKIP-equipped, access filter 403 (5) extends the tunnel to target server407, as described above.

Adaptive Encryption and Authentication Based on Data Sensitivity: FIGS.6 and 7

An important task in access control in a VPN is determining the minimumamount of security needed by a session. This is important first becauseat least that minimum must be guaranteed and second because moresecurity than is necessary wastes resources. The techniques employed inaccess filters 203 to determine the minimum amount are collectivelytermed SEND (Secure Encrypted Network Delivery). In SEND, access controldatabase 301 contains a data sensitivity level for each informationresource. The data sensitivity level indicates the level of secrecyassociated with the information resource and is assigned to theinformation resource by the security administrator responsible for theresource. An exemplary set of levels is Top Secret, Secret, Private, andPublic.

The levels used to indicate data sensitivity are also used to indicatethe trust level required for the access request. As previouslydescribed, access will be permitted only if the trust level determinedfrom the trust level of the technique used to identify the user, thetrust level of the path of the access request through VPN 201 or thetrust level of any encryption technique used to encrypt messages sentover the path is at least as great as the data sensitivity level for theinformation. The trust levels for user identifications, paths, andencryption algorithms are contained in access control database 301. Withregard to trust levels of paths, the VPN is divided into networkcomponents, each network component being a connected set of IP networksthat is separated from other components by access filters 203. Eachnetwork component has a name and a trust level. For example, an Internetcomponent will have the Public trust level, while an internal networkcomponent may have the Private trust level. The trust level of a givencomponent may be based on its physical security or on the use ofencryption hardware in the component. As each access filter 203 is addedto a VPN, a description of its connections to the components of the VPNis added to database 301. Included in this description are the trustlevels of the networks. Consequently, any access filter 203 can use itscopy of database 301 to determine the trust level of each component ofthe path by which a session will be carried between a client and aserver.

The trust level for a user is determined from the manner in which theaccess request identifies the user. In access control database 301, eachgroup of users has one or more identification techniques associated withit, and each identification technique has a minimum trust level. Thebasic techniques are:

-   -   Certificate via SKIP. A user is identified by the name in his or        her X.509 certificate used with the SKIP protocol to        authenticate and encrypt traffic.    -   Certificate via User Identification Client. A user is identified        by the name in his or her X.509 certificate transmitted to        attached access filters 203 via a special Conclave client module        called the User Identification Client. This transmittal is done        securely, using a challenge/response mechanism.    -   Windows Domain ID via User Identification Client. A user who        logs in to a Microsoft Windows Domain and has installed the User        Identification Client automatically has his or her Windows        identity, including group memberships, transmitted to attached        access filters 203. The logon to the network is done securely        within the mechanisms of the NetBIOS protocol.    -   Authentication Tokens. Authentication tokens (such as those        manufactured by Security Dynamics Inc. and Axent Corp.) may be        utilized in two ways: via the User Identification Client in an        out-of-band manner, or in-band within the Telnet and FTP        protocols.    -   IP Address and/or Domain Name. The IP address or fully qualified        domain name of the user's computer.

In a preferred implementation of SEND, the identification techniqueshave a predetermined order from most secure to least secure. Thetechniques just listed would be ordered are as they are in the abovelist, with the most secure techniques being at the top of the list. Theordering of the identification techniques is somewhat subjective, butreflects the general security of the identification technique and therigor applied to the distribution and validation of user identities. Anadministrator in VPN 201 then relates the ordered trust levels to theordered identification techniques. For example, if the administratorrelates the private trust level to identification by means ofauthentication tokens, a user who desires to access a resource with theprivate sensitivity level must identify himself or herself by means ofan authentication token or another identification technique which isabove the authentication in the order of identification techniques. Theadministrator of the access filter likewise orders the cryptographicalgorithms available in the VPN from most secure to least secure andrelates the ordered trust levels to the ordered cryptographic algorithmsand orders the network paths employed in VPN 201 and relates the orderedtrust levels to the ordered network paths. These relationships betweentrust levels and orderings with regard to security are included inaccess control database 301.

Then a SEND table is constructed which relates trust and sensitivitylevels to identification and encryption techniques. FIG. 6 is aconceptual representation of such a SEND table.

SEND table 601 has three columns: one, 603 for the trust/sensitivitylevels, one, 605, for minimum encryption methods, and one, 607, forminimum identification methods. For details on the encryption methods ofcolumn 605, see Bruce Schneier, Applied Cryptography, John Wiley & Sons,New York, 1994. Each row 609 of the table associates a trust/sensitivitylevel with a minimum encryption level for the path connecting the accessfilter, client, and server and a minimum identification level for theuser. Thus, row 609 (1) associates the “top secret” trust/sensitivitylevel with the 3DES encryption algorithm and a user certificate obtainedvia SKIP. A user who wishes to gain access to a resource with thesensitivity lever-top secret “must consequently have an identificationthat is certified by SKIP and if the path does not have atop secret”trust level, the session must be encrypted with the 3DES algorithm. Onthe other hand, as shown by row 609 (4), a user who wishes to gainaccess to a resource with the sensitivity level “public” may beidentified by any method and there is no requirement that the session beencrypted.

When a new session is initiated, the first access filter 203 in the pathemployed for the session proceeds as follows:

The access filter determines the information resource being accessed andlooks up its sensitivity level in database 301. The minimumauthentication for that sensitivity level from SEND table 601 specifieswhich identification mechanisms may be used by the access filter toidentify and authenticate the user making the access.

The first access filter 203 then consults database 301 to determine fromthe user groups the user belongs to and the information sets theresource belongs to whether the user may access the resource.

The first step is to determine from the access data base which of theidentification methods used to identify the user have trust levels highenough for the sensitivity level of the resource.

Then first access filter 203 consults database 301 using the user'sidentification according to each of the identification methods that hasa high enough trust level to determine the user groups that the userbelongs to.

First access filter 203 also consults data base 301 to determine whichinformation sets the resource belongs to.

Having determined the relevant user groups and information sets, firstaccess filter 203 consults data base 301 to locate the access policiesthat determine whether access is to be allowed or denied to the session.If at least one policy allowing access is found and none denying accessare found, the user is allowed access; otherwise, access is denied.Details of steps b, c, and d will be given below.

If access was not denied, the first access filter 203 then consultsdatabase 301 to determine the network components that make up the routethrough the VPN from the client to the server that contains theinformation resource. The route is considered as having up to threelogical segments:

Segment (a), from the client to the first access filter 203. Thissegment may or may not have been encrypted, depending upon whether theclient uses SKIP.

Segment (b), from the first access filter 203 to the access filter 203in the path nearest the server; and 3.

Segment (c), from the access filter 203 nearest the server to theserver; this segment also may or may not be encrypted.

If segment (a) and segment (c) exist, each will consist of a singlenetwork component. Segment (a) will not exist if the client is on thefirst access filter; segment (c) will not exist if the server is on theaccess filter nearest the server. If segment (b) exists, it will consistof one or more network components. Segment (b) will not exist if thereis only one access filter between the client and server.

For each of the segments:

-   -   For segment (a), any encryption must be done by the client. If        the trust level of segment (a) is not at least as strong as the        sensitivity of the resource, or if the trust level of the        encryption done by the client is not at least as strong as the        sensitivity of the resource, access is denied.    -   For segment (b), if the weakest trust level of any network        component in the path is greater than or equal to the data        sensitivity of the resource, then the traffic is sent without        encryption. This corresponds to the case where the network is        inherently secure enough to transmit the data. In the example        table above, information resources with a Public data        sensitivity level may be transmitted on any network, as shown by        row 609 (4). However, the access filters 203 will use SKIP to        authenticate the session, allowing subsequent access filters to        pass the session through without incurring the larger overheads        of decryption, access checking, and reencryption. If the weakest        trust level for the path is less than the data sensitivity of        the resource, then the SEND table is consulted for the minimum        encryption algorithm required for the sensitivity level and the        session is encrypted using that algorithm. The encryption        upgrades the security of the link, making it suitable to carry        data of that given sensitivity and permitting access by the user        to the resource.    -   For segment (c), the portion of the path from the access filter        203 nearest the server to the server, first access filter 203        determines the trust levels of segment (c) and of any encryption        used in segment (c) from information in database 301. If the        trust level of this segment of the path is less than the        sensitivity level of the information resource, and in that case,        if the encryption used in segment (c) is not at least as strong        as that required as the minimum level in the SEND table        considering the sensitivity level of the resource, then first        access filter 203 will deny access.

The above method of determining sensitivity and trust levels ensuresthat access filters 203 employ encryption only as necessary to achievethe necessary trust levels. This reduces the number of sessions thatwill be encrypted while keeping the description of network configurationin database 301 simple and manageable. The result is better scalabilitywith regard to both management of and performance in the VPN.

FIG. 7 provides an example of how the sensitivity level of aninformation resource, the trust level of the user identification, andthe trust level associated with the path between the client and theserver affect access by the user to the information resource. In FIG. 7,a SKIP-equipped user at client 703 initiates a session 701 to obtain aninformation resource 723 which is stored at SKIP-equipped server 705.

Segment (a) of the above discussion appears in FIG. 7 at 707; segment(b) appears at 709 (1 . . . 4); Segment (c) appears at 711. Informationresource 723 has a sensitivity level of “secret”. The first accessfilter 203 that the session encounters is filter 203 (1). Access filter203 (1) uses its copy of the access control database to determine thesensitivity level of resource 723. Here, the user has used a SKIPcertificate and an examination of SEND table 601 in data base 301 showsaccess filter 203 (1) that this kind of user identification meets therequirements for information resources having the “secret” sensitivitylevel, so segment (a) 707 has the required trust level. Consequently,the first access filter goes on to determine the trust level of segments(b) 709 (1 . . . 4) and (c) between access filter 203 (1) and server 705in the VPN. Segment 709 has subsegments 709 (1), 709 (2), 709 (3), 709(4), and 709 (5), and first access filter 203 (1) checks the trust levelof each of these subsegments in database 301. Segment 709 (2) isInternet 121, so its trust level is “public”, which is the minimum insegment 709. Then access filter 203 (1) uses access control data base301 to check the trust level of segment 711. It is “secret”. Thus, onlysegment (b) 709 has a trust level that is too low for the path of asession that is accessing a “secret” information resource 703. To dealwith this problem, access filter 103 (1) must encrypt the session tobring it up to the necessary trust level. First access filter 203 (1)consults SEND table 601 to determine what kind of encryption isrequired, and row 609 (2) indicates that DES encryption is sufficient.First access filter 203 (1) accordingly encrypts the session using thatalgorithm and sends it to access filter 203 (5).

In FIG. 7, segment 707 connecting client 703 to access filter 203 (1)has a trust level which is high enough for the resource's sensitivitylevel, and there is thus no need for client 703 to encrypt its request.When that is not the case, access filter 203 (1) will give client 703access only if client 703 has encrypted the request using an encryptionmethod whose trust level is sufficient for the sensitivity level of theresource. It is for this reason that roamer 503 in FIG. 5 must beSKIP-equipped. Since roamer 503 accesses access filter 403 (3) viaInternet 121, roamer 503's requests can never have more than the publictrust level unless they are encrypted, and in order to have full accessto the resources in VPN 201, roamer 503 must use an encryption methodsuch as the one provided by SKIP whose trust level is sufficient for thehighest sensitivity levels. In some embodiments of access filter 203,the access filter may negotiate the encryption technique to be used in arequest with the client in a manner similar to that which it employs inthe preferred embodiment to negotiate the user identification mode.

Overview of the Administrators' Interface to Access Control Database301: FIGS. 8-12

An access policy defines access in terms of user groups and informationsets; consequently, before an access policy may be defined, theadministrators must define the user groups and information sets; howthat is done is shown in FIG. 8. Defining a user group involves steps803 through 807: first the users are defined, then the user groups aredefined, and then the users are assigned to the proper user groups.Defining information sets involves steps 809 through 813: first theresources are defined, then the information sets are defined, and thenthe resources are assigned to the information sets. When this has beendone for the user group and information set involved in a policy, theaccess policy can be created, as shown at 815. As previously pointedout, the rights to define and determine the membership of user groupsand information sets and to make administrative policy for them aredetermined by the administrative policy, while the right to make accesspolicy for user groups and information sets are determined by the policymaker policy.

As can be seen from the foregoing, the user interface is generally usedto define relationships between two entities or sets thereof. Thegeneral form of the graphical user interface (GUI) for access controldatabase 301 corresponds to that task. The display includes two windows,each of which contains representations of entities that are to bebrought into relationship with each other, and the relationship isdefined by selecting the entities and where necessary, defining therelationship.

Defining User Groups: FIG. 9

FIG. 9 shows the display 901 for populating and defining user groups.Window 903 in the display contains a hierarchical display ofcurrently-defined user groups; window 903 is similar to those used todisplay hierarchies of files in the Windows 95 brand operating systemmanufactured by Microsoft Corporation. In window 903, user groups forwhich the administrative user using display 901 has administrativerights appear in black; the other user groups appear in gray. Above thetwo windows are two button bars 911 and 915. Button bar 911 lists thedisplays available for modifying access control database 301, whilebutton bar 915 lists the operations that may be performed on thosedisplays. Thus, the button label “user groups” in button bar 911 ishighlighted, indicating that display 901 is the one for populating anddefining user groups. With regard to button bar 915, when window 903 isactive, an administrative user with the right to administer a user groupmay modify the user group by selecting it in window 903 and using thedelete button in button bar 915 to delete the user group or the newbutton to add and name a new user group that is beneath the selecteduser group in the hierarchy. When the administrative user clicks onapply button 921, access filter 203 modifies its copy of access controldatabase 301 to conform with what is on display 901 and themodifications are propagated to all copies of access control database301 in the VPN.

Window 909 displays users. A set of user is indicated in the display bythe manner in which the user in the set identified. In this case, theusers are identified by IP addresses and they appear in the display asranges of IP addresses. Button bar 913 indicates the other kinds ofidentifications that can be displayed in window 909.

As with window 903, when the window is active, the new and deletebuttons can be used to add and delete users. To assign the user (s)specified by a user identification to a user group, the user of the GUIselects a user group, as shown at 917, and a set of identifications, asshown at 919, and then uses the add to group button in button bar 913 toadd the set of identifications to the group, as is shown by the factthat the range of IP addresses selected at 919 now appears in thehierarchy below the user group selected at 917. The effect of theoperation is to make users whose sessions have the source IP addresseslisted at 917 into members of the user group R&D, and when the userclicks on the apply button, all copies of access control database 301are modified accordingly.

FIG. 10 shows the display 1001 used to define information sets. Here,window 1003 contains a hierarchical list of information sets and window1005 contains a hierarchical list of the available resources. Thehierarchical list of information sets and the hierarchical list ofavailable user groups made in the same fashion as the list of usergroups. Again, information sets and available resources over which theuser of display 1001 has administrative authority appear in black; theother items on the list appear in gray. In window 1001, the availableresources are the Internet and the two locations that make up VPN 201.In a more developed VPN 201, the list of available resources wouldindicate servers at the location, services in the servers, and theinformation items provided by the services. For example, if the serviceprovides a directory tree, the information items contained in thedirectory tree would be indicated by means of a pathname which specifiedthe root of the directory tree and used wildcard characters to specifythe files above the root in the tree. When a resource is added to aserver, the resource may be defined via the 1005 window. Having thusbeen defined, a resource may be assigned to an information set in thesame fashion that a user identification is assigned to a user group.Again, clicking on the apply button causes the changes in display 1001to be propagated to all copies of access control database 301.

FIG. 11 shows the display 1101 used to define policies. Which type ofpolicy is being defined is specified in button bar 1113; as indicatedthere, display 1101 is defining access policy. All of the policydisplays have the same general format: a window 1103 which contains ahierarchical display of user groups, a window 1105 which contains adisplay of a hierarchy of objects for which policy may be defined and apolicy definition window 1107 which contains access policy definitions1108. In the hierarchy of objects, objects for which the user of display1101 has the right to define policies appear in black; the others appearin gray. In display 1101, what is being defined is access policies, sothe objects are information sets.

Each access policy definition has four parts:

-   -   an active check box 1117 that indicates whether the access        policy defined by the definition is active, i.e., being used to        control access;    -   the user group 1119 for which the access policy is being        defined;    -   the information set 1123 for which the access policy is being        defined;    -   and access field 1121, which indicates whether access is being        allowed or denied and thereby defines the access policy.

Menu bar 1109 and button bar 1115 permit administrators whom the policymaker policy allows to do so to edit, add, delete, and activate ordeactivate a selected policy definition 108. Active check box 1117 ofeach policy definition 1108 permits the administrator to activate ordeactivate the selected policy definition 1108; access field 1121permits the administrator to select either allow or deny as the policy.The delete button in button bar 1115 permits the administrator to deletea selected policy; the new button permits the administrator to make anew policy definition 1108; to do this, the administrator selects a usergroup in window 1103 and an information set in window 1105 and thenpushes the new button. The new access policy definition 1108 appears indisplay 1107, and the administrator can edit the new access policydefinition as just described. To apply a change to access controldatabase 301 and propagate it to all access filters 203, theadministrator clicks on apply button 1125.

Display 1101 also contains a policy evaluator tool which lets theadministrator see how the current set of access policy definitionsdetermines access for a given user group or resource set. When theadministrator clicks on the policy evaluation button in button bar 1113and selects a user group from display 1103, the tool displays theselected user group in blue and all of the information sets in display1105 which the policy definitions permit the user group to access ingreen and the remainder in red; all of the policy definitions which arerelevant to the determination of which information sets may be accessedby the user group are highlighted in the same set of colors. The samething happens if the administrator selects an information set; then theevaluator tool displays the selected information set in blue, all of theuser groups that can access the information set in green and the rest inred, and also highlights the relevant policy definitions. The user canalso select a policy. In that case, the selected policy appears in blueand the user groups and information sets affected by the policy inappear in blue or red, as determined by the policy. The user canadditionally select more than one user group, information set, orpolicy. In that case, the evaluator tool shows each policy that appliesto all of the selected items and the effects of those policies. Theevaluator tool can be turned off by clicking on policy evaluation inbutton bar 1113 and colors and highlights can be turned off inpreparation for a new policy evaluation by clicking on the resetevaluation button in button bar 1115.

FIG. 12 shows the display 1201 used to input information about an accessfilter 203 to access control database 301. Window 1203 shows ahierarchical list of the access filters 203; when the window is active,access filters may be added or deleted using the add and delete buttonsin button bar 1209. Window 1205 is used to input or display informationabout the access filter 203. The display in window 1207 is determined byclicking on a button in button bar 1207; as shown by the buttons,displays in window 1207 can be used to input and view information aboutaccess filter 203's network connections, to input and view informationabout the trust levels of those connections, to scan networks foravailable servers and services, to set up alerts for problems detectedin access filter 203, to specify optional parameter for software, and tospecify the distribution order of access control database 301 changes.The highlighting of alert setup indicates that display 1205 shown inFIG. 12 is the display used to display and establish alerts.

User Interface for Discovering Resources: FIGS. 18 and 24

The users of VPN 201 have an interface for seeing what resources areavailable to them in VPN 201. The interface, termed herein the IntraMapinterface (IntraMap is a trademark of Internet Dynamics, Incorporated),shows each user at least the resources that belong to the informationsets that the user may access according to the access policies for theuser sets the user belongs to. In other embodiments, the IntraMap maytake the sensitivity level of the resource and the trust level of theuser's identification into account as well.

The IntraMap interface is implemented by means of a Java applet thatruns on any Java-equipped World Wide Web browser. Using the Web browser,the user can scan the graphical display to find and access resourcesthat are available to the user or to request access to resources thatare not currently available to the user. Access by a user to a resourceis determined by the access policies that apply to the user and theresource. FIG. 18 shows the display 1801 produced by the IntraMapinterface. The left-hand side of IntraMap display 1801 shows a ResourceList 1803; the right-hand side of the display shows a Find field 1807, aSort section 1809, a Services section 1811, and a Description field1813. On-line help for using the IntraMap is available by clicking Helpbutton 1815.

Resource List 1803 shows resources and information available in VPN 201to the user who is using the IntraMap interface. The listing ishierarchical. The user can expand or collapse branches of the “tree” byclicking on the ‘+’ and ‘−’ markers on the branches. Each entry 1804 inthe list includes a name for the resource. The color used to display anentry indicates what kind of access the user has. If the entry 1804 isdisplayed in blue, the user has an active hyperlink to the resource andmay double click on the resource to have it displayed. If it isdisplayed in black, it is also available to the user, but no hyperlinkis available, so a separate application must be used to retrieve it.Resources displayed in gray are not directly available to the user, butif the user selects one, the IntraMap interface opens a dialog box thatpermits the user to send email requesting access to the administratorwho is responsible for access policy for the information set theresource belongs to. The administrator may then modify the access and/oradministrative policies as required to give the user access. Anadministrator may further give a resource the hidden property. When aresource has that property, it will appear in IntraMap interface 1801only if the user belongs to a user group that the access policies permitto have access to an information set that the resource belongs to. If aresource does not have the hidden property, it will always appear inIntraMap interface 1801. Otherwise, it does not appear. A resource mayhave a more detailed description than that contained in its entry 1804.The description is displayed in Description field 1813 when the userselects the resource.

In addition to resource list 1803, IntraMap display 1801 displays twospecialized resource lists at 1805:

-   -   What's New 1806 displays the latest information postings from        others within the enterprise. If an administrator has given the        user access to the What's New web page, the user may post the        URL of a new resource there.    -   What's Hot 1808 displays the enterprise's most popular        information resources, based on how frequently they are        accessed.

The service types control at 1811 lets the user filter the resourcesthat are to be displayed in resource list 1803 by the type of servicethat provides the resource. Each service type has a check box in servicetype control 1811. If the box is checked, the service type is includedand the resources associated with this service appear in the ResourceList. Otherwise, the resources associated with this service do notappear in the Resource List

The IntraMap interface lets the user sort Resource List 1803 byinformation sets, locations, or services. To do this, the user selectsthe way he or she wishes to sort the resource list in sort field 1809.The user may also specify the order in which the categories are used inthe sort. The interface further has a search function. To do a search,the user enters a search string in FIND field 1807. The resource listand the resource descriptions for the resources on it are then searchedin the order specified in sort field 1809. The search simply looks forwhole or partial word matches. It is not case sensitive. The first matchis displayed, and function keys may be used to navigate to othermatches. Of course, if a user has not checked a service type in servicetype field 1811, resources of that service type are not involved ineither sorting or searching.

FIG. 24 shows an implementation 2401 of the IntraMap interface. To theuser of VPN 201, the IntraMap interface appears as a Web page that isone of the resources provided by report manager 209 running on accessfilter 203 (c) of FIG. 2. A user in VPN 201 or even the general public(that is, someone who is a member of the Internet user group) may begiven access to the IntraMap interface in the same fashion as he or shemay be given access to any other resource. As will be clear from thefollowing description, the Web page for the IntraMap may be on anyserver in VPN 201. Implementation 2401 has components in workstation2403 used by the user to look at the IntraMap, components in accessfilter 203 (I) which is local to work station 2401, and in access filter203 (c), which is the access filter upon which report manager 201 runs.Of course, access filter 203 (c) may also function as a local accessfilter. Local access filter 203 (I) is connected to report access filter203 (c) by VPN 201 and workstation 2403 is connected to local accessfilter 203 (I) by LAN 213.

As will be explained in more detail later, all access filters 203 have alayered architecture. The bottommost layer is an Internet packet filter2419 that deals only with Internet packet headers. Packet filter 219reads the source and destination addresses in the Internet packetheaders and applies a set of rules to them. As determined by the rules,it either accepts them, discards them, or routes them further in VPN201. The rules also determine how the accepted packets are to be routedwithin access filter 203. The next layer of the architecture is serviceproxies 2427. The service proxies intercept traffic for services such asthe World Wide Web and do access checking on the traffic. If accessfilter 203 provides the service itself or does access checking for aserver that provides the service, IP filter 2419 sends packets intendedfor the service to a service proxy 2427 for the service. The serviceproxy uses access control database 301 to do protocol-level accesschecking for the service. For example, the service proxy for the Webservice may check whether the user making a request for a given Web pagehas access rights for the page.

The next higher level is services level 2425; if the relevant serviceproxy permits an access request and the access filter is also the serverfor the service, the request goes to the service at service level 2425to be processed. In the case of the Web page, the service would locatethe page and return it to the requestor. Two services are involved inthe IntraMap: the Web service and an IntraMap service. In FIG. 2401, theWeb service appears as WebS 2423. The proxy for WebS 2423 is WebP 2421;for reasons that will become clear in the following, the IntraMapservice has only a proxy, IntraMapP 2417. Additionally, access controldatabase 301 includes IntraMap information 2422, which is an optimizedversion of the information in access control data base 301 that servesas a basis for the IntraMap display.

The chief difference with regard to the IntraMap implementation betweenaccess filter 203 (c) and access filter 203 (I) is that access filter203 (c) includes a World Wide Web page 2410 with a copy of IntraMap Javaapplet 2411. When downloaded from access filter 203 (I) to Web client2429 in work station 2403, Java applet 2411 produces requests directedto IntraMap server 2425 and uses the results returned by IntraMap server2425 to produce IntraMap display 1801.

Operation is as follows: to the user of work station 2403, the IntraMapmay appear as a link to a Web page. Thus, to use the IntraMap, the useractivates a link to IntraMap page 2410. Web browser 2429 in workstation2403 responds to the activation of the link as it would to theactivation of any other link to a Web page: it makes a request for thepage and sends it to the server indicated in the link. In the case ofthe link to the IntraMap, the link specifies Web server 2423 in accessfilter 203 (c), so the request goes via local access filter 203 (I) andVPN 201 to access filter 203 (c). As with any other access to a resourcein VP 201, local access filter 203 (I) does access checking for theIntraMap page request. Since the request is for a Web page, the checkingis done by Web proxy 2421. In most VPNs 201, IntraMap page 2410 will beaccessible to any user in VPN 201, and access control data base 301 thusindicates that any user with a valid IP source address may accessIntraMap page 2410.

When the request is received in access filter 203 (c), IP filter 2419forwards it to Web proxy 2421, which in turn forwards it to Web server2423, which responds to the request by downloading IntraMap applet 2411to Web browser 2429 in work station 2403, where IntraMap applet 2411begins executing in Web browser 2429. During execution, it sends arequest to IntraMap proxy 2427 for IntraMap information 2422 Like allJava applets, IntraMap applet 2411 sends the request to the server thatit is resident on, in this case, access filter 203 (c). However, as withany other request from workstation 2403, the request goes by way oflocal access filter 203 (I). There, IntraMap proxy 2427 detects that therequest is addressed to IntraMap proxy 2427 in access filter 203 (c) andinstead of sending the request on to access filter 203 (c), obtainsIntraMap information 2422 from the local copy of access control database 301 in local access filter 203 (I), filters it so that it specifiesonly those resources belonging to the information sets to which the usergroups to which the user belongs have access to make to list 2431 andreturns it via LAN 213 to IntraMap applet 2411, which then uses list2431 to make IntraMap display 1801. In making the display, applet 2411applies any filters specified in the request and also sorts the list asspecified in the request. List 2431 not only indicates the resourcesthat are available, but also contains information needed to fetch theresource. Thus, if the resource has a hyperlink, the hyperlink isincluded in the list; if it is a resource for which the user presentlydoes not have access, but to which the user may request access, the listincludes the name and email address of the administrator for theresource.

Details of Access Control Database 301: FIGS. 13-17

In a preferred embodiment of access filter 203, access control database301 is implemented at two levels: one used by the graphical userinterfaces use to manipulate access control database 301 and anotherused in actual access checking. The first level is implemented using theMicrosoft Jet brand database system developed by Microsoft Corporation.The second is implemented using memory mapped files (MMFs) which arecompiled from the first-level data base. The following discussion willdescribe the first-level implementation and explain how the informationcontained in it is used in access checking. In reading this discussion,it should be remembered that actual access checking is done using theMMFs, as will be described in detail later.

As is the case with most database systems, the Microsoft Jet branddatabase system has a schema, that is, a description of the logicalstructure of the database. FIGS. 13-17 are displays generated by theMicrosoft Jet brand database system of the schema for access controldatabase 301. FIG. 13 shows the schema 1301 for the part of the databasethat defines user groups. The display is made up of two elements:representations of classes of tables 1303 in the database andrepresentations of links 1305, which show relationships between tablesbelonging to certain classes of tables. The representation of the classof the table shows the name of the class at 1310 and the data fieldsthat will be contained in each table belonging to the class at 1308.Each table instance has an ID assigned by the database system. The otherdata in the table varies with the class of table. A link is made betweena first table belonging to the first class of tables and a second tablebelonging to the second class of tables by using the ID of the secondtable in the first table and vice-versa. Thus, link 1305 shows thattables of the class User Group Tree table 1307 can be linked with tablesof the class User Groups table 1309. Some links have numbers at theirends. The numbers indicate the number of the links that the table at theend the number is located at may have. Thus, the link connecting thetable of class 1309 and the table of class 1307 has the number 1 at theend for the table of class 1309 and the number oo at the end for thetable of class 1307, indicating that any number of IDs of instances ofclass 1309 may appear in an instance of class 1307, but only one ID ofan instance of class 1307 may appear in an instance of class 1309.

User Group Tables: FIG. 13

User group tables 1301 contains a table of class user groups 1309 foreach user group in database 301. Data of particular interest in tablesof class User Groups 1309 include the group name, which is thecharacter-string name of the group, the group description, which is acharacter-string description of the group, and pre-defined information,which indicates among other things whether a user who is a member of thegroup is an administrator, i.e., can make administrative policy, asecurity officer, i.e., can make policy maker policy, or a simple userof information. User group tables 1301 further organizes the user groupsinto a hierarchy—both for the purposes of inheritance and also for thehierarchical display of user groups shown in window 903 of FIG. 9,associate identifications of users with the user groups, and associatealerts with the user groups. The organization into the hierarchy list isdone by means of tables of class User Group Tree 1307. Each table of theclass User Group Tree links a table of the class User Group to a parentuser group (also of the type User Group). Multiple User Group Treetables may exist for a particular User Group table, depending on thenumber of places in which a particular user group appears. As alreadymentioned, there are five different ways of identifying users to anaccess filter 203: by a range of IP addresses, by a fully-qualifiedInternet domain name, by the identity of the user in the MicrosoftWindows brand operating system, by an authentication token, and bycertificate. The table classes for the tables used to identify users bycertificates are shown as 1321. The table classes for the tables thatidentify users by a range of IP addresses are shown at 1317; those forthe tables that identify users by IP domains are shown at 1319; thosefor the tables that identify users by Windows brand operating systemID's are shown at 1315; and those for the tables that identify users byauthentication tokens (labeled as smart card in the figure) are shown at1323. The table classes 1325, finally, define tables for the informationused in alerts that are related to user groups. A table of User Groupclass 1309 may have associated with it any number of tables for any ofthe ways of identifying users. As this implies, a given user may beidentified in a number of different ways at once.

In order to perform an access check, access filter 203 must determinewhat user groups the user making the request belongs to. The requestincludes an identification for the user, and the identification is thestarting point for the determination. The tables in user group tables1301 permit access filter 203 to determine from the identification whatuser groups the user belongs to and from those user groups, thehierarchical relations that determine the other user groups the userbelongs to. Assuming that the user is identified by an IP address,access filter 203 begins by finding one or more tables of the IP RangeDefinition class (in 1317) which define ranges of IP addresses whichinclude the user's IP address.

Each of these tables has a link to a table of the IP Ranges class (in1317) which relates the range defined in the IP Range Definition classtable to a user group ID, which in turn serves as a link to a table ofclass User Groups 1309 for the user group corresponding to the range ofIP addresses. Each of the tables of class User Group has a link to atable of class User Group Trees, from which links can be followed to thetables of class User Groups for the user groups from which the usergroups specified by the IP addresses inherit access rights. Thus, at theend of the process, IP filter 203 has located all of the user groupswhich are relevant for determining whether the user may access theresource.

Moreover, IP filter 203 knows from the request how the user isidentified and can determine from that what level should be assigned tothe identification of the user used in the request. The information inuser group tables 1301 is compiled into MMFs. When a user initiates asession, the user provides a user identification to the first accessfilter 203 on the session's path; access filter 203 uses the useridentification with the MMFs to make a determination equivalent to theone explained above. Access filter 203 can thus determine for a givenuser identification whether it identifies a user that has access, whatkind of user identification it is, and therefore what trust level ithas, and which user groups the user belongs to. User group tables 1301thus contain all of the information needed for the user portion of anaccess policy 1108.

Information Set Tables: FIG. 14

FIG. 14 shows the schema 1401 for the tables that define informationsets. These tables relate information sets (resource groups in FIG. 14)to the resources that make them up and to the network locations of theresources and also organize the information sets into the hierarchicallist of information sets displayed at 1003 of FIG. 10. Each informationset in access control database 301 is represented by a table of classresource group 1403.

Tables of class resource group are organized into a hierarchy forinheritance and display purposes by tables 1419. The relationshipbetween an information set and the resources that make it up on one handand the locations in the VPN in which they are stored are established bytables of class resource group elements 1407. A table of class resourcegroup may be linked to any number of tables of class resource groupelements. A table of class resource group elements is linked to anynumber of tables of the classes Site Elements 1411, Services 1413, andResources 1409. There is a table of class Resources for every resourcerepresented in database 301. Included in the table are the resource'sID, its name, the ID for the service that provides it, an ID for adefinition of the resource's sensitivity level, a description of theresource, the email address of the administrator of the resource and ahidden flag which indicates whether IntraMap should display the resourceto users who do not belong to user groups that have access to theresource. The IntraMap interface obtains the information it needs abouta resource from the Resources table for the resource.

The tables of the classes Site Elements and Services, as well as thoseof the classes Sites 1415 and Servers 1417 belong to the classes 1421that describe the locations of information in the VPN. There is a tableof class Sites for every physical location in the VPN; there is a tableof class Servers for every server in the VPN; and there is a table ofclass Services for every service in the VPN. Links in the tables ofclass Site Elements relate sites to servers; links in the tables ofclass Servers relate the servers to the services they offer; and linksin the tables of class Services relate the services to the resourcesthat they host.

In determining what information sets a requested resource belongs to,access filter 203 begins with the information in the request. Therequest is contained in an IP packet, and consequently has a header anda body. In the header there is an IP address which specifies a locationin virtual network 201 and a server at the location, a port number whichspecifies a service on the server, and in the body, the description ofthe resource in the form prescribed by the protocol. For example, if therequest is for a Web page, the description of the resource will be theresource's URL. Access filter 203 uses the IP address to locate a tableof class Sites, uses the link in that table to locate a table of classSite Elements 1411. That table relates the site to the server IDS forthe servers at the site and access filter 203 uses the server IDS tolocate the tables of class Servers 1417 for the site's servers. It canthen use the IP address again to locate the table of class Serverscorresponding to the server specified in the request and can follow thelinks from the Server table to the tables of class Services for theservice and can use the port number from the request to find the properService table. Once it has found the proper Service table, it can followthe links to the tables of class Resources 1409 and locate the Resourcestable corresponding to the resource in the request. From there, there isa link to a table of class Resource Group Elements 1407 which relatesresources to the resource group identifiers for the information setsthey belong to. The resource group identifiers in turn specify tables ofclass Resources Group 1403, and these tables have links to tables ofclass Resource group Tree, from which the hierarchies of resource groupscan be determined to which the resource specified in the requestbelongs. Having done that, access filter 203 has found the resourcegroups that are relevant for determining whether the request should begranted. Resources table for the resource further contains thesensitivity level for the resource. Again, the information ininformation set tables 1401 is compiled into MMFs. When the requestreaches the first access filter 203 in the path between the user and theserver that provides the resource, the first access filter 203 uses theMMF files to make a determination that is the logical equivalent of theone just described. Thus, after examining the MMF files that contain theinformation from User Groups tables 1301 and Information Sets Tables1401, the proxy has determined the trust level of the useridentification, the sensitivity level of the information resource, theuser groups the user belongs to, and the information sets theinformation resource belongs to.

Policy Tables: FIG. 16

FIG. 16 shows the tables used in access control database 301 to defineaccess control policies; included in these policies are access policies,administrative policies, and policy maker policies:

-   -   Access policies relate user groups to resource groups;    -   Administrative policies relates a user group whose members are        administrators to one of:        -   1. another user group        -   2. an information set        -   3. a resource        -   4. a location (site) in the VPN        -   5. an access filter 203 or other server        -   6. a service    -   Policy maker policies relate user groups of administrators to        information sets.

Each policy relates a left-hand side, which is always a table of classUser Groups 1309, to a right-hand side, which, depending on the kind ofpolicy, may be a table of class Resources 1409, a table of classResource Groups 1403 (representing information sets), a table of classSites 1415, a table of class Services 1413, a table of class Servers1417, or a table of class User Groups 1309. Policy tables 1601 thus fallinto three large groups: left-hand tables 1603, policy tables 1605, andright-hand tables 1609. The right to change policies is hierarchical: amember of a user group whose User Group table indicates that it is agroup of a type of Administrators can change access policies asdetermined by the administrative policy for the group. In turn, thoseadministrators may specify other administrative policies related totheir sub-domain.

Corresponding to the three kinds of policies, there are three classes oftables in policy tables 1605: tables belonging to Policies Access class1611, Policies Administer class 1613, and Policies Policy Maker class1619. Tables of all of these classes share a number of features: theycontain the ID of the user group table for the left-hand side of thepolicy, the ID for the table representing the item specified in theright-hand side of the policy, an indication of the policy (accessallowed or denied), an indication of whether the policy is pre-definedand cannot be deleted, and an indication of whether the policy ispresently active. The difference between the classes is what can be onthe right-hand side of the policy, and therefore the links to theentities on the right-hand side; in the case of access policies andpolicy maker policies the right-hand entities are information sets only,and consequently, tables of the Policies Access and Policies PolicyMaker classes contain right-hand links only to tables of the ResourceGroups class, while tables of the Policies Administer class may containright-hand links to in the alternative tables of class User Groups,tables of class Resource Groups, tables of class Sites, tables of classServers, tables of class Services, and tables of class Resources.

The rights given the user group specified by the user group on theleft-hand side of an administrative policy over the sets of entitiesspecified by the right-hand side vary depending on the kind of entity,as shown in the following table:

Left-hand Right-hand side side Meaning of “allowed” Access User groupany Members of the user group can create administrative policies groupfor the target or included items. This allows for the delegation ofresponsibilities. User group User group Members of the user group canadminister the target user group, including nested user groups. Allowedadministration includes deleting, moving, and copying the target usergroup; nesting it in another user group; adding members to it; andnesting other user groups in it. User group Information Members of theuser group can administer the information set set, set including nestedinformation sets. Allowed set administration includes deleting, moving,and copying the target information set; nesting it in anotherinformation set; adding members to it; and nesting other informationsets in it. User group Site Members of the user group can administer thesite, including elements under it from the Available Resources list (allAccess Filters, servers, services, and resources). Allowedadministration includes deleting and moving the site; adding it to aninformation set; and adding locations and Access Filters to it. Controlover the Intranet location is necessary in order to define new AccessFilters. User group Access Filter Members of the user group canadminister the Access Filter, including elements under it from theAvailable Resources list (all servers, services and resources). Allowedadministration includes deleting and moving the access filter; adding itto an information set; and adding servers or services to it. User groupServer Members of the user group can administer the server, groupincluding elements under it from the Available Resources list (allservices and resources). Allowed administration includes deleting andmoving the server; adding it to an information set; and adding serversor services to it. User group Service Members of the user group canadminister the service, including resources under it from the AvailableResources list (all resources). Allowed administration includesdeleting, moving, and copying the server; adding it to an informationset; adding resources to it. User group Resource Members of the usergroup can administer the resource. Allowed administration includesdeleting, moving and copying the resource and adding it to aninformation set.The following table describes the rights given administrative usergroups when they appear on the left-hand side of a policy maker policy:

Left-hand Right-hand side side Meaning of “allowed” Access UserInformation Members of the user group can manage access group setpolicies set controlling access by any user group to the informationset, including nested information sets. They may also include theinformation set and any of its descendants in a further policy makerpolicy.As pointed out in the discussion of the Information Set tables above,the proxy that is doing the access checking can use the User Grouptables and the Information Sets tables to find the user groups the usermaking the access request belongs to and the information sets theinformation resource being accessed belongs to and can also use thesetables to determine the trust level of the user identification and thesensitivity level of the information resource. The proxy can thereuponuse the Policies Access tables to find whether any of the user groupsthe user belongs to may access any of the information sets theinformation resource belongs to. If any such user group is found, theuser may access the information set if the request's trust level is ashigh as the information resource's sensitivity level. To determine therequest's trust level, the proxy must determine the trust level of anyencryption technique being used and/or the trust level of the path inVPN 201 that is being used for the access. This information is availablein access filters tables 1701, shown in FIG. 17 and described below. Ifeither the access policies or the access request's sensitivity level donot permit the access, the message is disregarded and any session itbelongs to is dropped. The access checking process is substantially thesame when the request is a request by a user who is a member of anadministrative user group to access database 301, except that whenaccess is permitted, it may result in a modification of the database inaccordance with the rules set forth above. That modification will thenbe propagated to all other access filters 203 in VPN 201.

Server Tables: FIG. 17

FIG. 17 shows the schema for tables that are particularly significantfor the operation of servers in the VPN. There are three kinds ofservers in the VPN:

-   -   Plain servers. These are the servers upon which the resources        are stored and which execute the services by means of which the        resources are accessed.    -   Access filters 203.    -   Policy manager servers. These are access filters 203 that        additionally coordinate and distribute database 301 and/or        generate reports about operation and status of the VPN.

An access filter 203 may function additionally as a plain server.

There is a table of class Servers 1417 for every server in the VPN.Information in the table for each server included its ID, name, domainin the Windows NT brand operating system, its Internet name, whether itis an access filter 203 and additionally a policy server, whether accessto it is available only via an access filter 203, and whether it isinside the VPN. If the server is an access filter 203, it additionallyhas an identity that access filter 203 provides to other entities in VPN201 for purposes of authentication and encryption. In a preferredembodiment, the identity is the X.509 certificate for the access filterused by SKIP. The X.509 certificate also includes a public key foraccess filter 203. The public key may belong to one of a number of namespaces; the NSID (name space ID) is an identifier for the public key'sname space; the MKID (master key ID) identifies the public key withinthe name space. Also included in the table is a link to a table of classCertificate Authority 1711 that indicates the certificate authority thatissued the X.509 certificate for the access filter. Of course, serversother than access filters may also have X.509 certificates, and in thatcase, their Server tables will have the server's NSID and MKID.

Every plain server in the VPN has one or more services running on it.For example, an FTP service provides access to files (the resources) onthe server according to the file transfer protocol of the TCP/IPprotocol suite. Each table of class Servers 1417 for plain servers haslinks to a group of tables that define the services and resourcesavailable on the server. As shown at 1719, these tables include tablesof class Services 1413, which represent the services, tables of classResources 1409, which represent the resources available via theservices, and tables of class Service Definitions 1715 which define theservice.

The remainder of the tables for which FIG. 17 gives the schemas containinformation that is used by access filters 203. The tables whose classesare shown at 1705 contain information used by access filters 203 thatare policy managers to distribute database 301 and/or to generatereports; the tables whose classes are shown at 1717 contain informationabout optional parameters for the software being run by a given accessfilter 203; those whose classes are shown at 1709 contain informationabout the proxies and other software modules that access filters 203 useto do protocol-level access checking in access filter 203; and thetables at 1707 contain information about trust and sensitivitydefinitions for identifications of users and kinds of encryption.

The tables indicated by the reference number 1708 contain informationabout the VPN to which access filter 203 belongs. Access filter 203 usesthis information to route sessions and also to determine the trust levelof the path being used for a given session. Routing table class 1721defines tables that list the current routes to all networks accessiblefrom access filter 203. It is automatically updated as those routeschange. Attached Network class 1723 defines tables that indicate foreach access filter 203 the networks that access filter 203 is presentlyattached to; tables of that class contain links to tables of classNetwork Definition, which in turn contain a link to a definition intrust definitions 1707 which indicates the trust level of the network.The last class in this group is Point to Point Connection 1713, whichdefines tables that describe connections between access filters 203accessible via the VPN. There is a table for each combination of sourceand destination access filter 203 and a link to a trust definition thatspecifies the trust level of the path between the source and destinationaccess filters 203. The trust level in this table is based on theencryption technique used for messages traversing the path.

As previously explained, the User Group tables 1301 and the InformationSets tables 1401 provide the information needed by access filter 203 todetermine whether the access policies of tables 1601 permit the accessand also provide information about the sensitivity level of the resourcebeing accessed. Access filters tables 1701 additionally provide theinformation needed by access filter 203 to determine the minimum trustlevel of the path in the VPN being taken by the session and the trustlevels of the available encryption algorithms. Thus, if access filter203 determines that a given user wishing to access a given resourcebelongs to a user group which has the right to access the informationset to which the given resource belongs and that the authenticationlevel used for the user's identification is no lower than that requiredfor the resource's sensitivity level, access filter 203 can furtherdetermine whether the trust level of the path is sufficiently high, andif it is not, access filter 203 can raise the trust level the necessaryamount by selecting an encryption algorithm with the required trustlevel and encrypting the session.

Available Information Tables: FIG. 15

FIG. 15 shows the schema for available information tables 1501. Thetables are used by filter 203 to produce available resources display1005, shown in FIG. 10. The table classes shown at 1502 relate eachserver to its services and to the resources provided by the services.The table classes shown at 1504 organizes the available resources into ahierarchy for inheritance purposes and are also used to produce thehierarchical list shown at 1005, and by following the links from theSite Elements tables to the Servers tables, access filter 203 candetermine the hierarchy of sites, servers, services, and resources. Thetable classes at 1503, finally, establish a distribution tree of accessfilters 203. As will be explained in more detail later, when accesscontrol database 301 is modified, the tree defined by those tablesdetermines the order in which modifications are distributed to theaccess filters.

Modifying Access Control Database 301: FIG. 19

As previously mentioned, each access filter 203 has an exact duplicateof the copy of access control database 301 belonging to master policymanager 205 in access filter 203 (a) of FIG. 2. FIG. 19 shows how thatcopy of access control database 301 is modified and how themodifications are distributed from access filter 203 (a) to the otheraccess filters 203.

FIG. 19 shows access filter 203 (a) with master policy manager 205 andanother access filter 203 (i) at which an administrator using aworkstation is modifying access control database 301. The messages 1909needed to distribute and synchronize the modifications are encryptedusing SKIP and sent via VPN 201 using a protocol called the privatecommunications service (PCS). Each of the access filters has a number ofcopies of access control database 301. Any access filter 203 has at aminimum two copies: live database (LDB) 1907, which is the databasecurrently being used to do access checking, and mirror database (MDB)1905, which is a copy of the database that can be switched in to be usedin place of live database 1907. Thus, access filter 203 (a) has an MDB1905 (a) and an LDB 1907 (a) and access filter 203 (i) has MDB 1905 (i)and LDB 1907 (i).

If an access filter 203 is being used by an administrator to modifyaccess control database 301, then it will additionally have at least oneworking database (WDB) 1903. The working database is a copy of thedatabase that is not being used to control access and therefore can bemodified by the administrator. The administrator does so using aworkstation or PC connected via a network to the access filter. Theworkstation or PC displays the administrative graphical user interfacedescribed above, and the administrator uses the GUI to make the changesas enabled by administrative policies.

The changes may affect any aspect of the information stored in accesscontrol database 301. As indicated above, where the changes are changesin access or administrative policies, the administrator can use thepolicy evaluation feature to see the effect of the changes. When theadministrator is satisfied with the changes, he or she clicks on theapply button and the changes are distributed to all of the accessfilters and incorporated into each access filter's live database.

The process of updating all of the live databases is called databasesynchronization and distribution. The process has three phases:

-   -   First, the modifications are sent from the access filter 203        where they were made (here, access filter 203 (i)) to access        filter 203 to which the master database belongs (here, access        filter 203 (a)).    -   There, the changes are incorporated into the master database.        This is done by incorporating the changes into minor database        1905 (a), then swapping live database 1907 (a) and minor        database 1905 (a), and then changing the new mirror database        1905 (a).    -   Then, the changes are distributed from the Master Policy Manager        to other Access Filters.

At each access filter 203, synchronization is done in the same fashionas with access filter 203 (a). The order in which the changes are madein the access filters 203 of VPN 201 is determined by distribution tree1511, which in turn is set up using filters display 1201. The accessfilter 203 with master policy manager 205 is always the root of thetree. By default, the first access filter 203 installed in VPN 201 hasmaster policy manager 205. As other access filters 203 are installed,they are added to the tree as children of the Master Policy Manager.

The Master Policy Manager distributes changes to its childrensequentially. As each child access filter 203 receives its distribution,it then distributes to its children. This means that a shallowdistribution tree with many branches off the top level will complete adistribution cycle faster than a deep distribution tree with fewbranches off the top level. An administrator with the proper access canreconfigure the distribution tree to make distribution more efficient.

If two administrators have modified the same piece of information (forexample, an access filter definition) in different working data base1903, a synchronization conflict can occur. When this happens, masterpolicy manager 205 decides which modification to incorporate into accesscontrol database 301.

Optimizing Access Control Database 301: FIGS. 21 and 23

Although appropriate for persistent storage and use by administrationGUI 1915, database 301 is not optimized for use in real-time accesschecking. As will be explained in more detail below, access filter 203optimizes the data in database 301 that is required for run-time accesschecking and to make the display for the IntraMap. It does theoptimization each time a new copy of database 301 is received in accessfilter 203. In its optimized form, database 301 is a set of MemoryMapped Files (MMFs) in which the access policy information is stored ina form which permits quick access. The MMFs are so called because theyare generated as normal files, but then attached to a program's memoryspace and accessed by means of memory operations instead of fileoperations. A further optimization is achieved by using the MMF files togenerate rules that are used to do low-level filtering of messages by IPsource and destination addresses and port numbers for which access isallowed or denied.

FIG. 21 shows an example MMF file 2303. The MMF file in question isDBCertificatesbyUserGroupFile 2101, which maps the certificate matchingcriteria used to identify certificates that belong to particular usergroups to identifiers in database 301 of records for the user groupsspecified by the certificate matching criteria. File 2101 thus permits aproxy that has the certificate that identifies the source of a messagethat has been encrypted using SKIP to quickly determine the user groupsthat the user identified by the certificate belongs to. In the preferredembodiment, the certificate matching criteria are the O, OU, and CAfields of the X.509 certificate.

All MMF files 2303 have the same general form: there are two main parts:a header 2103 which contains the information being mapped from and adata part 2105 which contains the information being mapped to. Header2103 contains a list of entries 2107. Each entry contains a value beingmapped from (in this case certificate matching criteria (CMC) 2109) anda pointer 2111 to a record in data 2105 which contains the informationbeing mapped to (in this case, a list 2115 of identifiers 2113 indatabase 301 for the user groups that the user identified by CMC 2109belongs to). The entries in header 2103 are sorted by the informationbeing mapped from (here, CMC 2109), so that standard fast searchingalgorithms can be used to locate an entry 2107 corresponding to a givenset of certificate matching criteria.

FIGS. 23 A, B, and C provide a complete list of the MMF files 2301 thatare employed in one implementation of access filter 203. Therelationship between these files and the tables of database 301 will beapparent from the descriptions of the contents of the files provided inthe table. Each MMF file 2303 is represented by an entry in the tablewhich indicates the file's name and its contents. The files aresubdivided into groups 2311, 2313, 2319, 2321, 2323, and 2422. Files ofparticular interest are DBUsersFile 2307 and DBResourcesFile 2309, whichdescribe policies, DBCertificatesByUserGroupFile 2101, which is the MMFfile shown in detail in FIG. 21, DBResourceIDbyServiceIDFile 2315, whichrelates URLs of resources to resource IDS, DBResourcesbyResourceIDFile2317, which relates resources to resource groups, and DBTrustTableFile2325, which implements SEND table 601. Moreover, the following files areused to compile rules:

-   -   DBServerIDByNameFile    -   DBIPAndTypeByServerIDFile    -   DBServicePortToProxyPortFile    -   DBAttachedNetworksByServerIDFile    -   DBRoutingTableFile    -   DBRoutingTablebyServerIDFile        The files in IntraMap information 2422, finally, are filtered to        make list 2431, which is then downloaded to the client for use        by IntraMap applet 2411.

Details of Access Filter 203: FIG. 20

FIG. 20 is a block diagram of the architecture 2001 of an access filter203. In the implementation shown in FIG. 20, all of the components ofaccess filter 203 other than NIC cards 2013 are implemented in software.The software of the implementation runs under the Windows NT brandoperating system manufactured by Microsoft Corporation. The softwarecomponents fall into two broad classes: those that run as applicationsprograms at user level 2003 of the operating system and those that runat the kernel level 2005 of the operating system.

In general, the programs that run at the kernel level do IP-level accesschecking and encryption and authentication, while those that run at theuser level do application-level access checking. Also included in theuser-level components are software that manages access control database301 and software that produces the MMFs and rules for IP-level accesschecking from access control database 301. The following discussion willbegin with the kernel components, continue with the user-levelcomponents related to access control database 301, and will then dealwith the components for protocol-level access checking.

Kernel-Level Components

Network Interface Cards (NICs) 2013: These are the ethernet and tokenring cards installed in access filter 203. Three network cards aretypically configured. One is configured for the interface to theInternet, to a wide area network (WAN) 2011, or to a network connectedto another access filter 203. Another is configured for interface 2007to all client computers and a third is configured for interface 2009 tothe servers providing TCP/IP services. If there is no need for an accessfilter 203 to be interposed between clients and servers, there may beonly two NICs 2013, one to WAN 2011 and the other to a LAN. There willbe no need for the access filter to be interposed if no servers exist ataccess filter 203's location or if it is acceptable for all localclients to have access to all local information resources.

SHIM 2017: at installation time, a shim software module is insertedbetween two levels of the Windows NT brand operating system (the NDISand TDIS levels). This causes all traffic for particular protocols topass through SHIM 2017. In the implementation, all traffic for TCP/IPprotocols pass through SHIM 2017, while non-TCP/IP protocol traffic goesdirectly from the NIC to the appropriate other kernel modules. SHIM 2017invokes SKIP module 2021 as required to process the TCP/IP protocoltraffic.

SKIP module 2021: All IP network traffic is sent through SKIP module2021. If an incoming packet is not SKIP type, i.e., does not require theauthentication and decryption services performed by SKIP, then SKIPmodule 2021 passes it to IP filter module 2019. Similarly, if anoutgoing packet is not to be encrypted, then SKIP module 2021 sends itdirectly to the proper NIC 2013 for transmission. With SKIP-typepackets, authenticator 2024 in SKIP module 2021 serves to authenticate asession and encryptor/decryptor 2022 serves to encrypt and decryptinformation at a session level. Both authentication andencryption/decryption may be done with an arbitrary number of otheraccess filters 203, servers that employ SKIP, and clients that employSKIP. Authentication and encryption algorithms are set by IP filtermodule 2019 for outgoing packets based on SEND parameters or arespecified within incoming packets.

SKIP module 2021 maintains enough state information for each other sitethat it talks to so that it can maintain high-speed operation for mostSKIP-type packets. Packets are sometimes ‘parked’ while additionalprocessing (shared secret and temporary key calculation) is performed.‘skipd’ module 2037 in user space 2003 performs this extra processing.

IP Filter 2019: The IP filter operates on a set of rules that the rulescompiler, a component of database service 2029, makes from the accesspolicies in access control database 301. The basic functions of IPfilter 2019 are to:

-   -   1. Pass traffic up to the TCP/IP stack.    -   2. Block traffic-explicitly drop traffic for specific IP        addresses and according to special rules for emergency        conditions.    -   3. Drop traffic-implicitly drop traffic that neither matches any        rules nor is allowed by any policies.    -   4. Proxy traffic-rather than deliver traffic to the indicated        destination, route it to a proxy application on the current        machine.    -   5. Perform network address translation-change potentially        illegal internal IP addresses to legal ones.    -   6. Pass decisions off to pripf (discussed below) upon        establishing a new session for which access control cannot be        decided strictly by the rules. Typically, this is for sessions        that may be allowed by policies or by the VPN tunneling features        described previously.

IP filter 2019 performs these functions based on the followinginformation:

-   -   Rules generated by the rule compiler;    -   Source and destination IP address and port;    -   Encryption, or lack of it, on the incoming packet; and    -   Desired encryption and authentication on outgoing packets.        Components having to do with Database 301

Shared Directory 2028: VPN 201 uses a single access control database 301that is kept resident in each and every access filter 203. All versionsof database 301 in a given access filter 203 are maintained in shareddirectory 2028. Shared directory 2028 also contains each access filter203's log files.

Private Connect Service (PCS) Module 2025: PCS module 2025 providesaccess filter-to-access filter communications in VPN 201. All suchcommunications go through the PCS. The PCS has its own IP port numberand its messages must be encrypted. The particular functions carried outby means of PCS messages are:

-   -   Distribution tree management;    -   Distribution and synchronization of database 301;    -   Retrieval and distribution of routing table 1721;    -   Retrieval of Windows domain and user information;    -   Network scanning;    -   Retrieval of log contents; and    -   Transfer of files used by reporting and other subsystems.

ISDB Manager 2027: ISDB manager 207 manages database 301. It and the PCSare the only interfaces to the copies of database 301 in each accessfilter 203. It contains the software used to read and write all tablesin the copies of database 301.

DB Service and Rules Compiler 2029: DB Service 2029 produces MMF files2301. It does so each time a new copy of database 301 is received inaccess filter 203. It utilizes the functions provided by ISDB Manager2027 to read live database 1907 (I) for a given access filter 203 (I)and generate the MMFs 2301. A component of DB service 2029 is the RuleCompiler, which generates rules for use in the IP filter module fromrelevant ones of the MMFs 2301. The rules specify IP sources,destinations, and port numbers for which access is allowed or denied.The Rule Compiler exists as both a DLL and an application program thatsimply invokes routines in the DLL. In normal operation, the routines inthe DLL are invoked by the DB Service whenever a modified database 301is received in access filter 203 (I) from master policy manager 205. Theapplication program is used in special modes during the installation andbootstrapping process.

Memory Mapped Files (MMFs) 2301: As already explained, the MMFs 2301 aredata files generated by DB Service module 2029 and utilized by a numberof other modules in access filter 203. The files are designed to makethe following operations as efficient as possible:

-   -   Map from user identification to user group (5);    -   Map from information resource to information set (5);    -   Find policies that are associated with user groups; and    -   Find policies that are associated with information sets.

Components Related to Authentication

Evaluator 2036: Evaluator 2036 is a set of DLLs that are used by eachproxy in proxies 2031. Evaluator 2036 provides the following functionsto the proxies:

-   -   Prompting the user for further in-band or out-of-band        identification information;    -   Obtaining out-of-band authentication information from the        Authentication Tool Service (ATS);    -   Obtaining the certificate associated with the current user from        SKIPd;    -   Reading the MMFs 2301 and determining whether the access        policies permit the user to access the resource; and    -   Implementing the trust/sensitivity calculations for the path if        access is otherwise allowed, including deciding whether access        may be allowed via the path and if so, what encryption and        authentication is needed and which access filter is nearest the        server. These functions are performed by a component of        evaluator 2036 termed the VPN manager.

Authentication Tool Service/User Identification Client (ATS/UIC) 2039and 2041: ATS 2039 is the server in a client-server application thatgathers and authenticates user information. ATS 2039 runs on thecomputer upon which the other components of access filter 203 arerunning. The client part is UIC 2041, which runs on Windows-basedclients. ATS 2039 and UIC 2041 are the mechanism by means of whichaccess filter 203 obtains out-of-band authentication information. ATS2039 and UIC 2041 communicate by means of a session which is separatefrom the session being authenticated. ATS 2039 gathers and caches theauthentication information it obtains from the UIC clients and providesit to Evaluator 2046. The cached information from the clients includes

-   -   Windows ID;    -   Identity Certificates; and    -   Authentication token ID's.

SKIPd 2037: Most of SKIPd's functions are in support of SKIP 2021. Thosefunctions include:

-   -   change of certificate information with other communications        partners. This is done through the use of the Certificate        Discovery Protocol (CDP).    -   Calculation of the Diffie-Hellman shared secret. This shared        secret is key to the operation of SKIP. This calculation can        take a considerable amount of time and is saved to disk in an        encrypted form.    -   Calculation of the transport key used to encrypt the session.        These keys last for a period of time or amount of data.    -   In addition, SKIPd will provide certificate matching criteria to        the Evaluator (s) for use in user identification.

Proxies 2031 As previously explained, a proxy is software in filter 203that intercepts traffic for a particular protocol. The proxy‘understands’ the protocol that it is intercepting and can obtain theinformation required to identify the resources being accessed and/or toauthenticate the user from the messages that are being exchanged duringthe session. All of the proxies but SMTP receive messages on ports otherthan the standard ports for their protocol, with the IP filterredirecting messages using a given protocol from its standard port toits non-standard port. The proxy provides the information it hasobtained from the session to evaluator 2036 to decide whether the userhas access to the information resource. If the user does have access,access filter 203 forwards the incoming messages to the server to whichthey are addressed and the messages are processed further in the serverby the service for the protocol. In the following, each of the protocolsemployed in a preferred embodiment is discussed; of course, otherembodiments may include proxies for other protocols.

Pripf: The majority of network traffic occurs over a small number ofprotocols for which there are proxies in access filter 203. However,even where there is no proxy, an access decision must be made. In somecases, the decision can be made at the kernel level by IP filter 2019;when it cannot be, IP filter 2019 provides the traffic to pr ipf, whichobtains whatever information relative to user identification andinformation resources it can from the traffic and passes the informationto evaluator 2036 to determine whether access should be granted. Pripfis not truly a proxy, since it only makes an access determination for IPfilter 2019 and does not pass any traffic to standard protocol software.

FTP: The FTP proxy handles TCP/IP packets for the File TransferProtocol. In a present embodiment of VPN 201, access control is onlyenforced to the account (logon) level; in other embodiments, access maybe controlled to the file access level. During the FTP logon portion ofthe protocol, the proxy determines the server and account being accessedand provides this information to evaluator 2036 to determine whether theuser belongs to a user group whose members may access the informationsets corresponding to the account. The proxy further handles the in-bandauthentication using tokens in interactions with the user that arespecified in the FTP protocol.

FTP is actually a very complex protocol, involving both an active andpassive mode (used in Web browsers and some automated FTP clients). Inaddition, FTP data transfers utilize a second, dynamically determinedTCP session. This requires a special interface between the FTP proxy andIP Filter 2019 so that the FTP proxy can indicate to IP filter 2019 thatit should allow the second session.

HTTP: The HTTP proxy is built from the source code for the public domainCERN implementation of HTTP and contains all of its caching logic. Theproxy uses evaluator 2036 to check each access to a URL. No in-bandauthentications are performed with HTTP.

Telnet: The Telnet resource is only controlled to the server level dueto the non-standardized nature of Telnet logins. The Telnet proxy isonly used in order to provide additional in-band authentications. It isthe simplest of the true proxies.

NNTP: The NNTP (Network News Transfer Protocol) is used to control bothnews feed and news reading operations. During the feed operation, theNNTP proxy watches for uuencoded messages. These are binary messagesthat have been translated into ASCII text for the purposes oftransmission. Such messages are often broken up into multi-part messagesto keep them to a reasonable size. The NNTP proxy caches all parts ofbinary messages. For each such message, if that message is the last partthat will complete a multi-part message, then the entire multi-partmessage is assembled and anti-virus 2033 checks it for viruses asdescribed in more detail below. During the news reading operation,access is protected to the news group level. As in other proxies,evaluator 2036 is used to determine if the current user may access thenews group.

Real Audio: The Real Audio proxy allows clients to access real audioservers that are protected at the server level only. The real audioprotocol utilizes a standard TCP socket connection to establish asession, but then uses a return UP channel. As with FTP, the real audioproxy has an interface to IP filter 2019 that permits it to indicate toIP filter 2019 that the return UP channel is allowed.

SMTP: The SMTP (Simple Mail Transfer Protocol) differs from the otherproxies in that the IP Filter's proxy rules are not used to redirecttraffic to the SMTP proxy. Whereas the other proxies ‘listen’ on anon-standard port, the SMTP proxy listens on the standard port (25) andthen makes its own connections to the standard SMTP server software. Theaccess policies in database 301 must explicitly allow this access.

IntraMap: When a user specifies the URL for the IntraMap, report manager209 downloads the IntraMap Java applet and the downloaded appletattempts to make a connection back to a socket of the access filter 203that has report manager 209. IP filter 2019 of local access filter 203(I) intercepts the attempt to make the connection and provides it to theIntraMap proxy on local access filter 103 (I) The proxy responds toqueries from the applet by finding the answers in the local copy ofdatabase 301 and returning the answers to the applet, with all answersbeing filtered to reflect the user's access rights. The IntraMap proxyis not a true proxy in that the entire connection is always completelyserviced by the instance of the IntraMap proxy that intercepts theconnection.

Anti-Virus Module 2033

Anti-virus module 2033 in a preferred embodiment is a set of DLLsprovided by Trend Micro Devices, Inc., Cupertino, Calif. In otherembodiments, anti-virus modules from other sources may be used.Anti-Virus module 2033 checks all data entering VPN 201 for viruses. Inorder to provide the user with feedback on the progress of the transferand to prevent the user's client program from timing out, the data istransferred to the client and is copied at the same time into atemporary file used for virus checking. The last portion of the data,however, is not sent to the client until after virus checking iscomplete. As soon as the last portion is in the temporary file, thetemporary file is checked for viruses. If no viruses are detected, theremainder of the data is sent to the client. If a virus is found, thenthe transfer is aborted. In a present embodiment, the user is notifiedof a failed transmission. If an administrator has so specified, an alertmay be sent to the administrator.

Launch, Log, Alert and Reports 2027

The components of this module perform the following functions:

-   -   Launch-controls the initial sequence of startup tasks that takes        place on an access filter 203 when VPN 201 is established.    -   Logs-a DLL that provides a standardized logging interface.    -   Alerts-a standalone program that watches all of the NT logs,        looking for alert conditions specified in database 301. The        method by which an alert is delivered is specified using the GUI        for defining alerts.    -   Reports-a subset of the logs are forwarded to a special report        log, concentrated into a database and later forwarded to Report        Manager 209.

Administrative Graphical User Interface 1915

The GUI may run on access filter 203 or on any computer having a 32-bitWindows brand operating system that is attached to access filter 203.Whether the GUI runs on access filter 203 or on an attached system, itutilizes ISDB MANAGER 2027 to read from and write to a working copy 1903of access control database 301. All necessary modifications to accesscontrol database 301 are made through GUI 1915. An ‘apply’ operation inthe GUI is sent as a signal to PCS 2025, which responds to the signal bystarting the previously-described distribution and synchronizationoperation.

Detailed Example of Operation of Access Filter 203: FIGS. 5 and 22

In the following, the end-to-end encryption example of FIG. 5 will beexplained in detail. In that example, a roamer 503 whose PC is equippedwith SKIP is accessing a SKIP-equipped server 407 inside a site on VPN201. When roamer 503 was set up to access VPN 201, it was set up to doso via access filter 403 (3) using a particular type of encryption.Here, it will be assumed that the type of encryption being used byroamer 503 has a trust level of “secret” and that the user wishes toaccess a Web page on server 407 that has a sensitivity level of“secret”. Since what is being accessed is a Web page, roamer 503 isusing the HTTP protocol for its session with the HTTP service on server407. Since roamer 503, the access filters 203 in VPN 201, and server 407are all equipped with SKIP, they are all provided with their own publicand private keys. At a minimum, roamer 503 also has the certificate andpublic key for access filter 403 (3) to which it directs messages forservers internal to VPN 201; access filter 403 (3) has the certificateand public key for roamer 403 (or obtains them using the CertificateDiscovery Protocol); all access filters 203 in VPN 201 have or can geteach others' public keys and the public keys for servers in VPN 201 thatare equipped with SKIP. Additionally, each access filters 203 in VPN 201knows the IP addresses of all of the other access filters 203 andservers in VPN 201.

All of the messages which are sent and received as part of the HTTPsession between roamer 503 and server 407 are encrypted andauthenticated by SKIP. FIG. 22 shows the form taken by such a SKIPmessage 2201. The SKIP message is made by SKIP software on the systemwhich is the source of the SKIP message. SKIP message 2201 shown here isfrom roamer 503. Its main components are:

Outer IP header 2203: Outer IP header 2203 is used to deliver the SKIPmessage to access filter 403 (3). Contained in outer IP header 2203 area source IP address 2209 for roamer 503 and a destination IP address2206 for access filter 403 (3). Destination address 2206 used by roamer503 was set to specify access filter 403 (3) when roamer 503 was set upto access VPN 201. Source IP address 2209 may be dynamically assigned toroamer 503 by the Internet service provider that roamer 503 uses toconnect to Internet 121. Outer IP header 2203 further contains a messagetype (MT) field 2208 which specifies that the message is a SKIP message.

SKIP header 2205: SKIP header 2205 contains the information needed todecrypt SKIP message 2201 when it is received. SKIP header 2205 containsat least a destination NSID 2215 and destination MKID 2213 for thedestination's certificate, that is, the certificate for access filter403 (3), and the source NSID 2219 and source MKID 2217 for the source'scertificate, that is, the certificate for roamer 503. In addition, SKIPheader 2205 contains identifiers for the algorithm used to authenticatethe message (MAC ALG 2226) and the algorithm used to encrypt the message(CRYPT ALG 2225), as well as an encrypted transport key for decryptingthe message (Kp 2223) and an identifier 2224 for the algorithm used todecrypt the transport key.

Authentication header 2211: Authentication header 2211 contains a MAC(message authentication code) 2221, which is computed according to theMAC algorithm identified in field 2226 and which is used by accessfilter 403 (3) to verify that the message arrived without tampering.

Encrypted payload 2227: Encrypted payload 2227 contains the encryptedmessage which roamer 503 is sending to server 407, including IP header2331 for that message and encrypted message 2229. IP header 2331 has theIP address for server 407 and the port number for the HTTP protocolservice. Encrypted payload 2227 can be decrypted by using Kp 2223 withthe decryption algorithm specified by CRYPT ALG 2225.

Handling SKIP Message 2201

SKIP message 2201 arrives on Internet interface 2011 of access filter403 (3). Processing of the message begins at the SHIM level in kernel2005. SHIM 2017 sends all incoming traffic to SKIP 2021, which in turnrecognizes from MT field 2208 that the message is a SKIP message. Todecrypt and authenticate the message, SKIP needs to decrypt Kp, and todo that it provides SNSID 2219, SMKID 2217, DNSID 2215, and DMKID 2213to SKIPd 2037, which uses the IDs to retrieve the certificates forroamer 503 and access filter 403 (3) from SKIPd 2037's certificatecache. If a certificate is not there, SKIPd 2037 uses the CDP protocolto fetch the certificate. The information in the certificates is thenused together with access filter 403 (3)'s private key to create ashared secret value, which is then used to decrypt transport key Kp 2223and to produce two internal keys, Akp and Ekp. SKIP securely saves theshared secret for use with future messages, since its computation takesa significant amount of time. Next, a MAC is computed for the entirereceived message and the Akp is used with MAC 2221 and MAC ALG 2226 toverify that entire message 2201 has not been tampered with. If that isthe case, the key Ekp is used to decrypt encrypted payload 2227 torecover the original message from roamer 503. Decrypted payload 227 isthen provided to IP filter 2019, which applies its rules to the sourceIP address, destination IP address, and port number of IP header 2231.If no rule denies access, IP filter 2019 follows another rule andredirects the unencrypted message together with SNSID 2219 and SMKID2217 to the port for the HTTP proxy. IP filter 2019 uses theDBServicePortToProxyPortFile of MMFs 2301 to find the port in question.

Processing continues at the application level in user level 2003 of theoperating system. The HTTP proxy has in hand the IP address of theserver, the port number of the service, the URL for the Web page, thecertificate belonging to the user of roamer 503, and the encryptionmethod used to encrypt the message. It will use evaluator 2036 todetermine the following from the MMF files 2301:

-   -   the user groups that the user represented by the certificate        belongs to;    -   the information sets that the Web page belongs to;    -   whether there is an access policy that permits at least one of        the user groups to access at least one of the information sets;        and    -   whether the trust level of the message is at least equal to the        sensitivity level of the Web page.

Beginning with the first of these tasks, evaluator 2036 receives theNSID and MKID for the certificate and uses the certificate matchingcriteria from the certificate with the DBCertificatesByUserGroupFile toobtain the identifiers for the user groups the user sending the messagebelongs to.

Evaluator 2036 determines the information sets by taking the IP addressof the server, the port number of the service, and the URL for the Webpage and using the IP address with the DBServerIDByIPFile to determinethe server that contains the Web page, the port number with theDBServiceIDByPortFile to determine the service on the server thatprovides it, and the URL with the DBResourceIDbyNameFile to get theidentifier for the resource in database 301, and then uses theDBResourcesByResourceIDFile to get the identifiers for the informationsets that the Web page belongs to. With the identifiers in database 301for the user groups and information sets in hand, evaluator 2036 usesthe DBResourcesFile to determine whether there is an access policy whichpermits any of the user groups that the user belongs to access any ofthe information sets that the Web page belongs to. In so doing, it mayonly consider user groups whose membership is determined using modes ofidentification whose trust levels are sufficient for the resource'ssensitivity level. The DBResourcesFile maps each information setidentifier to a list of the user groups for which there are accesspolicies involving that resource set. For each user group, theDBResourcesFile further indicates whether the policy allows or deniesaccess. Evaluator 2036 uses the DBResourcesFile to determine for eachinformation set in turn that the Web page belongs to whether the list ofuser groups for which there are access policies with regard to theinformation set includes one of the user groups to which the userbelongs. If there is an access policy for any of the user groups thatdenies access, the evaluator indicates to the HTTP proxy that access isdenied; if there is no access policy for any of the user groups thatdenies access and at least one that allows access, the evaluatorindicates to the proxy that access is allowed; if there is no accesspolicy of any kind for any of the user groups, the evaluator determinesif there is at least one certificate or token based user group that hasan allow policy for the resource. If so, and the requesting client has aUIC running, then the UIC is contacted to ask the user for additionalidentity information; if additional identity information comes back, theprocess described above is repeated. Otherwise, the evaluator indicatesto the HTTP proxy that access is denied.

Of course, evaluator 2036 will also deny access if the access requestdoes not have a trust level equal to the sensitivity level of the Webpage. Evaluator 2036 obtains the sensitivity level of the Web page fromthe DBResourcesByResourceIDFile, the trust level of the useridentification from DBTrustAuthenticationsFile, and the trust level ofthe encryption method from the DBTrustEncryptionsFile. Since SKIP hasencrypted the message with a method that has the “secret” trust level,the trust level of the path through the network is not of concern inthis example. To determine whether the trust levels for the useridentification and the encryption method are sufficient for thesensitivity level of the Web page, Evaluator 2023 uses theDBTrustTableFile, which effectively implements SEND table 601. If thetrust levels are sufficient, Evaluator 2036 indicates to the proxy thatthe access is allowed.

Once the proxy has confirmed that access is to be allowed to theinformation resource specified in the message, the proxy originates anew session to the actual service, the HTTP service on server 407. Proxy2031 sends a special message to IP filter 2019 telling it to allow thespecific session through, since otherwise this session would probably beblocked by rules or sent again to a proxy. The message to IP filter 2019also includes information about the encryption needed for the newsession, which in this example is that the session should be encryptedto the final access filter 403 (5) and should use encryption suitablefor the data sensitivity level, which is secret. When IP filter 2019encounters the new session, it finds that it matches the criteriaspecified by proxy 2031, so it passes the session to SKIP. Sinceencryption is needed for this session, the message will be reencrypted.SKIP 2021 creates a SKIP message 2201 in the same fashion as describedabove, except that:

-   -   Outer IP header 2203 for the message specifies access filter 403        (3) as the source of the message and access filter 403 (5) as        the destination;    -   SKIP header 2205 has SNSID 2219 and SMKID 2217 for access filter        403 (3) and DNSID 2215 and DMKID 2213 for access filter 403 (5),        and the other values in header 2205 are also those required by        the fact that the source and destination for the message are now        access filter 403 (3) and access filter 403 (5);    -   Encrypted payload 227 is the same as before (except that it has        been encrypted using a different key) and MAC 2221 is produced        as required for entire new message 2201.

As the proxy is relaying the message it is also watching for filetransfer types that might contain viruses. When it encounters one, itapplies anti-virus software 2033 to these files. If a file contains avirus, the proxy fails to deliver the complete file, thereby renderingthe virus harmless. If access control database 301 so indicates, theproxy sends an alert when anti-virus software 2033 detects a virus.

As new SKIP message 2201 is received at access filter 403 (5), it ispassed to SKIP 2021, where it is authenticated and decrypted asdescribed previously. By the same mechanism as described above withregard to access filter 403 (3), IP filter 2019 on access filter 403 (5)recognizes that the message is destined for the HTTP applicationprotocol, so it directs it to HTTP proxy 2031. That proxy accepts themessage, then sends information it can obtain about the message'soriginator (access filter 403 (3) from outer IP header 2203 and SKIPheader 2205 to evaluator 2036 to determine whether the session beinginstigated by this message should be allowed to proceed. Evaluator 2036examines the source IP address of the message as well as the otheridentity information, and by looking up the source IP address in the MMFfile DBServerIDByIPFile, determines the identifier in data base 301 foraccess filter 403 (3), uses that identifier to locate access filter 403(3)'s certificate, and finds that certificate information matches theretrieved certificate associated with access filter 403 (3)'s messagebeing processed. The source of the message, access filter 403 (3), isthereby recognized as an access filter 403 within VPN 201, so evaluator2036 responds that the session should be allowed, for the reason that itis a message already permitted by another access filter 403 within thesame VPN 201. This decision to allow the message is returned to the httpproxy 2031. The evaluator 2036 will instruct http proxy 2031 on accessfilter 403 (5) to allow any request that comes over the same session,for the same reason. As the http request is processed, the proxy willestablish an outgoing connection to the http service on server 407, inthe same manner as the outgoing session was established on access filter403 (3).

When the connection is initiated to server 407, evaluator 2036 looks upthe IP address of server 407 in the MMF file DBServerIDByIPFile todetermine the identifier in database 301 for server 407, uses theidentifier to locate the table for the server, and uses the certificateidentifier from that table and the DBCertificatesFile to find thecertificate for server 407. Then it uses the keys for access filter 403(3) and the public key for server 407 (obtained from the certificate) toconstruct a SKIP session as described previously. The actual message isencrypted and authenticated, a SKIP header 2205 is added, and an outerIP header 2203 is added, directing the message to server 407.

When the message reaches server 407, SKIP in server 407 checks theauthentication on the message, decrypts it, and forwards the decryptedmessage to the HTTP service, which performs the access to the Web pagerequested by the message contained in the payload. Having obtained theWeb page, the HTTP service makes a return message with an IP headerspecifying roamer 503 as the destination. This return message is thenencapsulated in a SKIP message 2201 as previously described. This SKIPmessage is directed to access filter 403 (5) and contains theinformation in outer header 2203 and SKIP header 2205 that is requiredfor a message between those entities.

When the reply message reaches access filter 403 (5), it isauthenticated and decrypted by SKIP 2021 there, and forwarded to IPfilter 2019. The message is found to match an existing session soevaluation is not needed; it is forwarded directly to HTTP proxy 2031.There it is checked for validity as an HTTP protocol reply message andretransmitted back to the originator of the HTTP session, which isaccess filter 403 (3).

Checking by the anti-virus module 2033 is not done since the originatorof this session is known to be another access filter 403 in the VPN 201,as it is known that access filter will do the checking if needed. Theretransmission of the reply is again processed through SKIP 2021 andencrypted as above, using the SKIP parameters required for an exchangebetween access filter 403 (3) and access filter 403 (5).

When this reply message reaches access filter 403 (3), precisely thesame thing occurs, that is, the message passes through SKIP 2021 and IPFilter 2019, to the http proxy 2031. There it is checked for validity asan HTTP protocol reply message, possibly passed through the anti-virusmodule 2033 (if the message content type warrants it), and retransmittedback to the originator of the HTTP session, which is roamer 503. Thetransmission of the reply is again processed through SKIP 2021 andencrypted as above, using SKIP parameters as set forth above for amessage being sent from access filter 403 (3) to roamer 503. The replymessage is then received at roamer 503, where it is authenticated anddecrypted by SKIP, provided to the user's browser, and displayed for theuser.

Generalization of the Techniques Employed in Access Filter 203

The techniques employed in access filter 203 have been generalized intwo ways:

-   -   Separation of policy evaluation from policy enforcement, which        permits entities other than access filters to enforce policies;        and    -   the policy database now not only permits definitions of users,        groups of users, resources, and groups, but also of new types of        user identification, new types of actions for which policies may        be defined, and new types of resources.

The following discussion will first describe how policy evaluation maybe separated from policy enforcement and then describe how the typesused to define policies may be extended.

Separation of Policy Evaluation from Policy Enforcement: FIGS. 20,26,and 27

FIG. 26 is a block diagram of a policy enforcement system 2601 in whichpolicy evaluation has been separated from policy enforcement. In system2601, the notion of policy has been generalized to include not onlyaccess policy, administrative policy, and policy making policy, but anyaction which a user may perform on an information resource. For example,a policy may state that a particular user group may print documentsbelonging to a particular information set.

System 2601 has Five Main Components:

-   -   requesting entity 2603, which requests that the action be        performed on the information resource, and which may be any        entity that can belong to a user group;    -   policy enforcer 2609, which can control performance of the        requested action;    -   resources 2611 (0 . . . n), which may be any information        accessible to or device controlled by policy enforcer 2609;    -   policy server 2617, which determines whether the action is        permitted; and    -   policy database 2619, which contains the policies from which        policy server 2617 determines whether the action is permitted.

Requesting entity 2603, policy enforcer 2609, and policy server 2609 caneach be located anywhere. The only requirement is that there be messagetransmission media between requesting entity 2603 and policy enforcer2609 and between policy enforcer 2609 and policy server 2617. The mediumbetween requesting entity 2603 and policy enforcer 2609 permitsrequesting entity 2603 to send a message 2605 requesting that an actionbe performed on a resource 2611 (i) to policy enforcer 2609 and receivean action response message 2607 from enforcer 2609 indicating whetherthe action was taken and if so the result. The medium between policyenforcer 2609 and policy server 2617 permits policy enforcer 2609 tosend a policy request 2613 to policy server 2617 requesting policyserver 2617 to indicate whether the policies in policy database 2619permit a given requesting entity to take a given action with respect toa given resource and policy server 2617 to respond to policy request2613 with a policy response 2615 which indicates whether the policies dopermit the action specified in the policy request.

It should further be noted that the action controlled by policy enforcer2609 need not even be performed by a component of the computer system.For instance, policies in the policy database might control access bylibrary patrons to books and the action specified in a policy might behaving a library page fetch a book from the stacks.

The forms of the policy request messages 2613 and the policy responsemessages 2615 are defined by a policy protocol. Examples of standardpolicy protocols that are presently being developed are COPS (CommonOpen Policy System) and RADIUS (Remote Authentication Dial In UserService, Internet standard RFC2138).

Policy server 2617 obtains the information necessary to make policyresponse 2615 and then provides the response to enforcer 2609. Policyserver 2617 includes a policy server database 2619 which containspolicies including one or more policies for the action which requestingentity 2603 has requested policy enforcer 2609 to perform on a resourceR 2611 (i). Policy server 2617 queries policy server database 2619 tolocate the relevant policies and then applies them to policy request2613. Doing this may require policy server 2617 to obtain otherpolicy-related information 2623 from any location accessible to policyserver 2617. One example of this process is the technique described inthe discussion of access filter 203 by means of which access filter 203obtains additional identification information about a user. If theinformation which policy server 2617 obtains from policy server database2619 and other sources indicates that the action is permitted, policyserver 2617 sends a policy response 2615 that so indicates and policyenforcer 2609 performs the action as indicated at 2610 and returns theresult via action response 2607 to requesting entity 2603; if policyresponse 2615 indicates that the action is not permitted, policyenforcer 2609 sends an action response 2607 indicating that the actionis not permitted.

An important advantage of separating policy enforcer 2609 from policyserver 2617 is that policy enforcer 2609 may be implemented at manydifferent levels within a system, where system is to be understood toinclude systems made up of devices connected by networks. Policy server2617 may contain policies for any policy enforcer, and consequently, theactions which may be governed by policies are no longer restricted toactions taken at one or two levels of a system.

FIG. 27 shows a system 2701 with components that are connected by meansof networks including a public network 2702 and an internal network 103.At the highest level, system 2701 has one or more policy decision points2723, which determine whether a policy permits an action, and one ormore policy enforcement points 2721, in which the decisions of thepolicy decision points are enforced. A policy decision point willinclude a policy server 2617 and a policy enforcement point will includea policy-enabled device, that is, a device which can function as apolicy enforcer 2609.

Communication between policy decision points and policy enforcementpoints is by means of policy messages 2725, which include policyrequests 2613 and policy responses 2615. When an entity 2603 requeststhat an action be performed using a resource 2611, the action will beperformed by a device controlled by a policy enforcement point 2721,policy enforcement point 2721 will exchange policy messages 2725 with apolicy decision point 2723 to determine whether the action is permitted,and if it is, policy enforcement point 2721 will cause the action to beperformed.

Included among the policy enabled devices in system 2701 are:

-   -   a policy-enabled router 2713, which enforces policy at the level        of routing traffic in a physical network;    -   policy enabled attached device 2719, which enforces policy at        the level of a device attached to the network of system 2701. An        example is a printer which is able to consult policy server 617        to determine whether to accept a print request from a certain        entity 2603.    -   policy enabled application program 2717, which enforces policy        at the level of the application program.

Each of the policy enabled devices deals with policy in the same fashionas described for policy enforcer 2609: when the policy enabled devicereceives an action request 2703 for which it must determine whether itconforms to the access policies established in policy database 2619, itsends a policy message 2725 to policy server 2617 and when it receives apolicy message in response, permits or denies the action as indicated bythe policy message.

Continuing in more detail about the levels at which the policy-enableddevices of FIG. 27 work, policy-enabled router 2713 may maintain tablesof permitted sources and destinations for the packets it routes; whenrouter 2713 is initialized, these tables are set up from informationprovided by policy server 2617; from then on, when router 2713 receivesa packet with a source or destination that is not in its tables, itsends a policy message 2725 to policy server 2617 indicating the sourceor destination, and policy server 2617 responds to the message byindicating whether the source or destination is to be included in thetables. Of course, router 2713's tables may also be kept updated bymessages sent by policy server 2617 to router 2713 when policy data base2619 changes. As can be seen from the foregoing, router 2713 does policychecking at the level of IP filter 2019 in implementation 2001 of accessfilter 203.

Policy-enabled attached device 2719 is a device such as a printer whichis attached to the network. The device is able to respond to a requestby an entity to use it with a policy message to policy server 2617 andto proceed according to the information it receives from policy server2617. Such policy-enabled devices 2719 permit a much finer granularityof control over such devices than is possible with access checking atthe level of access filter 203.

Policy-enabled application 2717, finally, permits policy enforcement ata higher level than was possible with access filter 203. As long aspolicy data base 2619 contains policy information relevant to theresources being accessed by an application program, policy-enabledapplication 2717 can exchange policy messages 2725 with policy server2617 and can thereby determine whether to permit or deny the actionwhich the user of policy-enabled application 2717 is requesting. Oneexample of a policy-enabled application 2717 is one which implements anInternet service such as FTP, HTTP, or SMTP. This is the level which ishandled by proxies 2031 in FIG. 20. Because the services may now bepolicy-enabled, proxies are no longer necessary; instead, thehigher-level Internet protocol can simply be passed on to the system onwhich the service resides that will provide the access requested by theprotocol. As shown in FIG. 27, the service can then itself exchangepolicy messages 2725 with policy server 2617 to determine whether therequested access should be permitted.

Another example of a policy-enable application 2717 is a documentprocessing program. In this case, policy database 2619 may containpolicies specifying sets of users that have the right to modify sets ofdocuments. When the user employs the program to select a document forediting, the document processing program can exchange policy messages2725 with policy server 2617, and if the policy response from policyserver 2617 indicates that the user may not modify the document, thedocument processing program may so indicate to the user and refuse topermit the user to modify the document.

As may be seen from the foregoing, the separation of policy evaluationfrom policy enforcement and the extensibility of policy definitionstogether permit virtually any operation that a program can perform on aresource to be the subject of a policy, and thus makes access controlsystems like those shown in FIG. 2701 not only scalable and easy tomanage, but easily adaptable to any present or future devices orprograms.

It should be pointed out here that policy evaluation and policyenforcement were logically separate in access filter 203, even thoughboth were contained in the same device. When FIG. 20 is looked at interms of FIG. 26, it is apparent that GUI 1915, launch, log, alertreports 2027, databases shared directory 2028, ISDB manager 2027, PCS2025, and MMFs 2301 implement a policy server 2617, while the remainingcomponents implement a policy enforcer 2609 that operates at the IPfilter and Internet protocol levels.

Generalization of Policy: FIG. 28

In access filter 203, an administrator with the proper access coulddefine new users and user groups, could define new resources andinformation sets, and could add services and servers. An administratorcould not define actions other than access to information.

Further, the ways in which one could define new user groups were fixedand resources were limited to sources of information. In the generalizedpolicy server of the preferred embodiment, these limitations have beenremoved. It is now possible for administrators define new actions, newways of defining user groups, and resources that are not informationsets. Of course, the right to make such definitions is itself determinedby policies in policy database 2619, as explained with regard toadministrative policies and policy maker policies in access filter 203.In most systems, definitions of types of entities, types of resources,and types of actions would be restricted to those people who belonged tothe user group Security Officer.

These new possibilities are illustrated in generalized policy syntax2801 for policy statements shown in FIG. 28. Generalized policy syntax2801 describes how policies will appear to administrators in the windowsfrom which the policies may be manipulated. In FIG. 28, the items initalics are the components of the policy statements that may be definedby an administrator of policy server 2617 who has the necessary accessto policy database 2619. The items in square braces are the words whichrelate the items in italics to define a policy. For example,

Employees are allowed to Access the HR Web Site

where Employees is a user group, Access is an action, and HR Web Site isan information set and the policy statement permits any user who belongsto the user group Employees to access any resource that belongs to theinformation set HR Web Site.

Continuing in more detail with generalized policy syntax 2801, Entityrepresents a user group whose members are defined by one of thetechniques employed in access filter 203 or by a technique defined by anadministrator of policy server 2617; The only requirement for the entityis that it be recognizable by policy enforcer 2609. Action represents anaction which may simply be access as in access filter 203 or an actiondefined by an administrator of policy server 2617; the only requirementfor the action is that policy enforcer 2609 be able to cause the actionto be performed on a resource. Resource represents an information set.In the generalized policy server, however, an information set may be aset of devices such as a printers or file servers. The only requirementfor a resource is that policy enforcer 2609 be able to cause the actionto be performed on the resource.

TimeIntervals 2809 permits the administrator to define a temporalrestriction on the policy that is being specified using generalizedpolicy syntax 2801. When policies are being evaluated to determinewhether a given user has access to a given resource, a policy that has atime interval is considered only if the time of evaluation is within thetime interval. For example:

Employees are allowed to Access the HR Web Site from 9:00 am-5:00 pmweekdays which limits access by employees to the HR Web Site to normalbusiness hours. In a preferred embodiment, a TimeInterval may be definedas follows:

-   -   ranges of starting to ending times of day,    -   ranges of starting and ending dates,    -   restriction on days of the week and holidays: options to include        or exclude specific days of week, and/or dates that are listed        as holidays,    -   restriction on weeks of month, allowing specification of every        week, every X weeks (where X is a number from 2 to 12) with a        starting reference date, or a list of week numbers within each        applicable month,    -   list of applicable months of the year        ActionAttribute (s) 2811 are administrator-defined definitions        of the manner in which the action permitted by the policy        statement may be carried out. Again, the only requirement is        that policy enforcer 2609 be able to carry out the action as        specified by the action attribute. For example:

Marketing is allowed to print to the Marketing Printer with type=colorThis policy contains the action attribute type=color, and the policypermits users belonging to the user group Marketing to do color printingusing the resource Marketing Printer.

Additional examples of action attributes are:

-   -   class of service required for the network connection;    -   route or media type to be used;    -   billing rate to be applied;    -   maximum quantity for this transaction;    -   maximum time allowed to complete the transaction.

As indicated by the syntax [with|when], time intervals can be used withaction attributes as well as with entire policy statements. Forinstance, a policy that places a time limitation on a class of servicelooks like this: Everyone is allowed to access the World Wide Web withbandwidth=90% when weekends This permits entities in the user groupeveryone to access the Web with bandwidth=90% weekends. When a timeinterval has been applied to an action attribute, the action specifiedin the policy is performed as specified in the action attribute only ifthe request to perform the action is made within the time interval thatis applied to the action attribute.

Implementation of Generalized Policies: FIGS. 29 and 30

FIG. 29 shows policy database 2901. Policy database 2901 is amodification of policy database 301 to accommodate the generalizedpolicies defined by syntax 2801 and to work in an environment wherepolicy evaluation and policy enforcement have been separated. Thus, inFIG. 29, policy query 2939 comes from policy server 2617 instead ofaccess filter 203 and includes a specifier of the action to be performedas well as a specification of the information source or other resourceupon which the action is to-be performed. The results 2941 of the queryare returned to policy server 2617. In addition to an indication ofwhether the policies permit the action, the results now include thevalues of attributes relevant to the action. The elements of FIG. 3whose functions remain unchanged in FIG. 29 have the reference numbersthat they had in FIG. 3.

Beginning with access policy 307, the first additional item ofinformation is access types definitions 2929, which define additionalclasses of actions for which policies may be defined in access policy307. Next, there is attribute information 2927, which defines attributesthat may be attached to entities involved in carrying out a policy.Included within attribute information 2937 are the following kinds ofinformation:

-   -   attribute assignments 2937, which specifies what user groups,        information sets, sites, or services an attribute is to be        employed with.    -   attribute labels 2941, which define the names the attributes are        known by in the user interface; and    -   attribute features 2939, which actually define how the attribute        affects the user groups, etc. that it is assigned to.

Schedules information 2925 defines time intervals that may be attachedto policies or to attributes. Within schedules information 2925,schedule rules 2931 actually define the time intervals; holidays 2933 isa table of holidays used in schedule rules. Resource types 2935 definesthe types of resources for which policies may be defined, and User IDtypes 2937 defines the types of identification required for entities forwhich policies may be defined.

In a preferred embodiment, database 2901 is implemented using MicrosoftCorporation's well-known MicrosoftX Access database software. Access isa relational database, that is, the information in the database isstored in tables. A utility in the Access software provides images ofthe tables and their relationships to each other.

FIGS. 13-17 and FIG. 30 of the present application are derived fromthose images. In FIG. 30, tables which appear in FIGS. 13-17 have thereference numbers which they bear in those figures; new tables havereference numbers beginning with “30”. Tables 3001 in FIG. 30 show howthe tables used to define time intervals and attributes are integratedinto policy database 2901. More generally, they show how a policy may bemodified by the addition of further elements and how new types ofelements may be defined for policies.

Detailed Implementation of Time Intervals

Beginning with the time intervals, these are defined in time intervaltables 3025. The tables include a schedule definition table 3023 whichdefines the names that may appear in TimeInterval (s) 2809 ingeneralized policy syntax 2801 and a schedule rules table 3025 whichdefines scheduling rules that can be associated with the names definedin ScheduleDefinition table 3023. More than one scheduling rule may beassociated with a given name. ScheduleDefID relates each scheduling ruledefined in table 3025 to the schedules that use the rule in table 3023;the fields Day Mask through End Date define the scheduling rule. Thefield Description gives a description of the rule and its purpose.

As mentioned above, time intervals may be defined for entire policiesand for attributes in policies. Thus, each policy defined inPoliciesAccess table 1611 now includes a SchedulDefID field. Each suchfield contains an identifier ScheduleDefID for a definition in table3023 of a time interval that is to be applied to the policy. Thus, whenpolicy server 2617 is determining whether a policy is applicable to anaction request, it can locate the time interval applying to a policy viathe ScheduleDefID field for the time interval in the entry in table 1611for the policy. Similarly, AttributeAssignment table 3007, which relatesattributes to user groups, resource sets, sites, or services, includes aScheduleDefID field for any time interval applicable to that particularassignment of the attribute. The mechanism for defining time intervals,finally, is also used in a preferred embodiment for scheduling alerts,and thus entries in table 3023 are also locatable from AlertSchedulestable 3021.

Detailed Implementation of Attributes

The tables used to define attributes and relate them to the user groups,resource groups, sites, and services that they may be applied to areshown in attribute tables 3003 in FIG. 30. A given attribute is definedby entries in the tables AttributeLabels 3005, Attributes 3011, andAttributeFeatures 3009. AttributeLabels table 3005 defines the labelsused for the attributes in ActionAttribute (s) in policy definitionsyntax 2801. There is an entry for each such label, the entry includingthe label itself, a description of the attribute, the precedence of thelabel, and the type of the attribute. The precedence of the labeldefines which attributes will apply when more than one is connected withthe policy evaluation. When one assignment has a higher precedence thanthe other, the one with the lower precedence is ignored. Each attributelabel entry is identified by an AttributeLabelID.

Each entry in the table Attributs 3011 gives a current definition of anattribute. The definition may have one or more AttributeLabelID fieldsidentifying entries in AttributeLabels table 3005. The label defined bythat entry in AtrributeLabels represents the attribute defined by theentry in Attributs 3011. The current meaning of the attribute is definedby the fields in table 3011. Included are a description of theattribute, its type, the ID of the server it applies to, and the devicetype on the server. The fields AttributeFeatureID and Value1 and Value2are of particular interest. There must be at least oneAttributeFeatureID field. The field identifies an entry inAttributeFeatures table 3009 which defines kinds and ranges of valuesused in the attribute. Value1 and Value2 define either a current singlevalue (Value1) or a current range of values (both Value1 and Value2)selected from the kinds and ranges of values defined for the attributein AttributeFeatures table 3009.

As will be apparent from the foregoing, AttributeFeatures table 3009 canbe used to define new kinds of attributes. Each entry in table 3009includes the identifier AttributeFeatureID used to locate the entry andfields as follows:

-   -   Class, the name of the class to which the attribute belongs (for        example, quality of service, billing rates, or maximum quantity        for a transaction);    -   Feature ID, a number that uniquely defines the feature within        its class;    -   Name, the name by which users know the feature;    -   Description, a description of the feature    -   Value Type, a definition of the type (s) of values that define        the attribute (for example, whether a single value or a pair is        necessary, and data type information;    -   Feature Precedence, an indication of the order in which features        will be applied in evaluating an attribute;    -   Value Precedence, an indication of whether the highest or lowest        value of a range is to be selected; and    -   Restrictions, an indication of restrictions on the values.

To define a new class of attributes, an administrator who is permittedby the policies of policy server 2617 to do so simply defines featuresfor the new class in AttributeFeatures table 3009 and then beginsdefining attributes that use those features. A feature may be anythingthat is meaningful for the policy enforcer 2609 which will be enforcingthe policy. It should be noted here that the general techniquesdescribed above for defining new kinds of attributes may be employedelsewhere in policy database 2901 to define new actions, new ways ofidentifying users, and new types of resources.

Once an attribute has been defined by information in tables 3005,3011,and 3009, it is related to an entity to which the attribute may apply.This entity is termed the attribute's subject. AssignmentID table 3007specifies these relationships. Each entry in table 3007 relates theattribute specified in its AttributeLabelID to a single subject;additionally, it may relate the attribute to a user group whose membersmay perform an action involving the subject. If the entry does notspecify a user group, the attribute applies to any use of the subject;otherwise it applies only when the specified user group uses thesubject. The subjects may be user groups, sets of resources, sites, orservices as specified by the values of the fields UserGroupID,ResourceGroupID, SiteID, and Server ID. Further fields in table 3007indicate whether the attributes are active (i.e., to be currentlyapplied), when application should start, when it expires, and if theattribute involves a time interval, a ScheduleDefID value for the timeinterval. The Precedence field indicates the precedence that theattribute will have among the attributes assigned to a given entity.

In deciding which attributes to apply in making a policy decision,policy server 2617 proceeds as follows: When policy evaluation iscomplete, the attribute assignments in table 3007 are searched for linksto any of the user groups, resource groups, sites, or services connectedwith the policy evaluation. If the entity performing the action belongsto a user group for which the attribute applies, the links from theattribute assignments 3007 are followed to the attribute labels in table3005 and in turn to the attributes in table 3011 and finally to theattribute features in table 3009. Each of these linked tables (exceptfor 3011) contains precedence information, which is used to determinewhich attributes in table 3011 of those discovered by following all thelinks will actually apply to the evaluation.

These precedences are considered separately for attributes of each classas defined by the attribute features in table 3009. Within each class,first the precedences in the attribute assignments in table 3007 areconsidered. Only those assignments with the highest precedence value areconsidered further, though all assignments sharing the same precedenceare considered. Next, the label precedences in the attribute labels intable 3005 of the remaining linked attributes are considered. Only thoselabels with the highest precedence value are considered further, thoughall labels sharing the same label precedence are considered. Next, thefeature precedences in the entries in AttributeFeatures table 3009 ofthe remaining linked attributes are considered.

Only those attributes sharing the highest feature precedence areretained. Finally, for each attribute in table 3011 that is linked tothe same entry in AttributeFeatures table 3009, the value precedence inAttributeFeatures table 3009 is used-to determine which attribute fromtable 3011 to use, by indicating whether the highest or lowest value isto be selected.

At this point, at most one attribute defined in table 3011 for each ofthe relevant attribute feature entries in table 3009 will remain, andthe values and features in these entries will be returned for use inevaluating the policy. In some cases, the request may indicate whatattribute values are desired and the request may be refused if they donot match those specified in the policy; in others, the attribute valueswill be provided to policy enforcer 2609 for use in performing theaction.

Optimizing Attribute Tables 3003 and Time Interval Tables 3025

As described in the discussion of access filter 203 above andillustrated in FIGS. 21 and 23, policy server 2617 in a preferredembodiment optimizes policy database 2901 by generating MMF files 2303from it. In the preferred embodiment, two new MMF files have been addedto optimize the information in tables 3003 and 3025. The two new MMFfiles are the following:

-   -   DBPropertiesFile: Contains all “properties”-attributes and        schedules—that can apply to other objects. This index is indexed        by PropertyID in those other objects.    -   DBPropertiesMetaDataFile: All properties have a name. This file        is indexed by property type name (with one entry in the index        for each property name contained in DBPropertiesFile) and maps        the names to a list of PropertyID's to enable them to be quickly        looked up in DBPropertiesFile.

User Interface for Time Intervals: FIGS. 31-33

FIGS. 31-33 show the window employed in the graphical user interfaceused in a preferred embodiment to see what time intervals (or schedules)have already been defined, to define a rule for a time interval, and toassociate a time interval with a policy. Beginning with FIG. 31, thatfigure shows a window 3102 used to display the defined schedules.Subwindow 3103 lists all of the defined schedules by name; subwindow3106 lists all of the defined rules by name. The displayed informationcomes from ScheduleDefinition table 3023 and ScheduleRules table 3025.

To see what rules a schedule name represents, the user selects the namein subwindow 3103, as shown at 3105, where Non-working Hours has beenselected. This schedule has two component rules, one for days of theweek, shown at 3107, and one for Saturdays, Sundays, and holidays, shownat 3109. When the schedule name is selected, the rule (s) belonging toit are highlighted in window 3106. Conversely, when a rule is selected,the schedule names for the schedules that use the rule are highlighted.Shown at 3111 in subwindow 3106 is the rule for business hours, anotherof the schedule names in subwindow 3103.

To make a new schedule, one clicks on New while subwindow 3103 is activeand enters the new schedule name and then selects the new schedule nameand highlights the rules belonging to it in subwindow 3102. To changethe rules assigned to a schedule, one selects the schedule name and thenselects different rules for the name in subwindow 3106. To make a newrule for an existing schedule, one selects the schedule's name andclicks on New, at which point the new rule can be made as describedbelow. One can also click on New while in subwindow 3106, create the newrule, and then relate the new rule to a schedule name as describedabove. A rule can also be related to a schedule name by dragging therule to the schedule name and dropping it on the schedule name.

The window used to make a new rule is shown at 3201 in FIG. 32. This isthe window for modifying an existing rule or making a new rule. Tomodify an existing rule, one double clicks on it. Inputs in the windowpermit the user to define the interval of time which is being applied tothe policy or attribute in terms of times of schedule validity (3203),days of the week for which the selected times are valid (3205), weeksfor which it is valid (3207), and parts of the year for which it isvalid (3209). As shown, window 3201 defines the schedule shown in FIG.31 at 3111. That schedule is represented by Business Hours. Theinformation shown in window 3201 is from ScheduleRules table 3025, andmodifications made using window 3201 are applied to that table.

FIG. 33 shows the window used to add a time interval to the definitionof a policy. Window 3301 restricts access by users belonging to the usergroup Corporate to the information set Corporate to the scheduleindicated at 3303 to be Business Hours. When the user clicks on box3303, the entire list of defined schedules is shown, and the user mayselect one or add a new name. When the user clicks on Definition button3305, window 3201 for the selected policy is displayed. If a new name isbeing added, the user fills in window 3201 as required for the newschedule. In terms of FIG. 30, selection of a schedule in FIG. 33 causesa field ScheduleDefID in PoliciesAccess table 1611 to be filled in withthe identifier for the entry in ScheduleDefinition table 3023 whichcontains the schedule's name in its Name field. If the schedule name isnew, a new entry is added to table 3023 for the new name. If a rule isadded or modified, then ScheduleRules table 3025 is modified as well.

User Interface for Attributes: FIGS. 34-37

The user interface for attribute definition and assignment is similar.FIG. 34 shows a window 3401 which lists the presently-defined attributesof the quality of service (QoS) type. These attributes determine howmuch bandwidth will be available to an access being made according to agiven policy. At 3401 are listed the attribute labels or names. here,four QoS attributes are defined, three for bandwidth amounts (High,Medium, Low), and one (Top Priority) for priority in case of conflicts.All of these attributes have a precedence of 0, as shown at 3405. Thebandwidth attributes are all defined by the Bandwidth feature, as shownat 3407. Value1 for each attribute is defined at 3409. Only Top Priorityhas a Value2. As specified in window 3401, the QoS attribute Highreceives a maximum bandwidth of 512000, Medium a maximum bandwidth of64000, and Low a maximum bandwidth of 32000. With Top Priority, thepriority specified for the attribute must lie between the valuesspecified for Value1 and Value2. The information in window 3401 comes ofcourse from tables 3005,3011, and 3009.

FIG. 35 shows window 3501 used to assign a QoS attribute to a usergroup, information set, site, or service. In subwindow 3503 is shown howthe QoS bandwidth attributes Medium, High, and Low (3509) have beenassigned to the subjects World Wide Web service, file transfer service,and remote access service respectively (3511) for all user groups (3507)and how the QoS priority attribute High has been assigned to the subjectFinance user group. The different assignments reflect the fact thatbandwidth is an attribute of a communications service, while priority isan attribute of a user of the communications service. Thus, within thebandwidth available for the Web service, members of the Finance usergroup will have high priorities. As shown by. this example, more thanone action attribute may apply to a policy. Further assignments ifattributes to subjects can be made by selecting user groups and subjectsfrom subwindows 3513 and 3515 respectively. The selections made in thiswindow are of course applied to table AttributeAssignments 3007. Window3503 can further be used in the same general fashion as window 3102 toreach the windows used to define attribute labels and features.

FIG. 36 shows the window 3601 used to read, modify, or make an entry inAttribute labels table 3011. Here, the entry being read is for theMedium QoS bandwidth attribute. At 3603 are shown the values of theentry's Label, Description, and Label Precedence fields. Anadministrator with the proper access rights can of course change thevalues of these fields via window 3601. At 3605 is shown informationfrom the entry in Attributs table 3011 for the attribute associated withthe label. There is shown the current value of Value1 in the entry andthe name of the feature. The feature name of course comes fromAttributeFeatures table 3009 for the attribute. Again, these values maybe edited via window 3601. Button 3607 is used to view a window thatshows the complete contents of the feature's entry in AttributeFeaturestable 3009.

FIG. 37 shows that window. Window 3701 is the window used to define newfeatures for a given class of attributes and new classes of attributes.The window of course works on the values of an entry in AttributeFeaturetable 3009. Box 3703 is a list of the classes of attributes; new classesmay be defined by adding to the list. Box 3705 is the name of thecurrent feature; between them, the class and the name, corresponding tothe fields Class and Name in the entries in table 3009, uniquelyidentify an entry. In this case, the entry is for the QoS Priorityattribute. Description box 3707 contains the value of Description in theentry being examined. 3709 indicates which value type the feature has,here a pair of values, as indicated in FIG. 34. At 3711 are shown thecurrent settings of the fields Feature Precedence and Value Precedence,and at 3713, any restrictions will appear.

CONCLUSION

The foregoing Detailed Description has disclosed to those skilled in thearts to which the Detailed Description pertains the best mode presentlyknown to the developers of the generalized policy server disclosedherein for implementing the generalized policy server. As describedabove, two fundamental features of the generalized policy server areseparation of policy evaluation from policy enforcement andextensibility with regard to the types of actions for which policy canbe made. With the separation of policy evaluation from policyenforcement, the policy enforcing components can be located at differentlevels in the system to which the policies apply and the policyevaluation components may be at locations that are remote from thelocations of the policy enforcing components.

While the techniques of separating evaluation from enforcement and ofmaking policies extensible with regard to the kinds of actions that canbe performed may be applied to any mechanism for defining policy, theyare particularly useful when employed in policy enforcement systemswhere policy is defined in terms of actions and sets of entities. Insuch systems, the types of entities which may perform actions and thetypes of entities upon which actions are performed may be madeextensible as well.

Further features of the policy enforcement system disclosed herein whichincrease the usefulness of the system are action attributes, whichdefine the manner in which an action authorized by a policy are to beperformed and time intervals, which define times at which a policy isvalid or at which an attribute is to apply to an action. A graphicaluser interface provides for easy definition and manipulation of policiesand their components.

As will be immediately apparent to those skilled in the relevant arts,many of the techniques described herein may be applied in any kind ofpolicy enforcement system and even those which are most useful in apolicy enforcement system that defines policies in the manner describedherein may be implemented in many different ways.

For example, different graphical user interfaces may be used, thepolicies may be implemented using different database systems, and withina given database system, different arrangements of tables may be used.Thus, an unlimited number of other embodiments of the principlesdisclosed herein are possible and for that reason, the DetailedDescription is to be regarded as being in all respects exemplary and notrestrictive and the breadth of the invention disclosed herein is to bedetermined not from the Detailed Description, but rather from the claimsas interpreted with the full breadth permitted by the patent laws.

1. A method for controlling access to network information, the methodcomprising: storing a local copy of one or more policies in memory, theone or more policies limiting access to the network information;receiving a request from a user concerning access to information in anetwork; executing instructions stored in memory, wherein execution ofthe instructions by a processor: determines that the user is authorizedto access the requested network information based on at least the localcopy of the one or more policies, identifies a path through a pluralityof devices in the network, the plurality of devices including a serverhosting the requested network information, a plurality of accessfilters, and a user device associated with the user, and encrypts amessage containing the requested network information for transmissionbetween the server and a first access filter from the plurality ofaccess filters, wherein a plurality of transmissions of the messagebetween device pairs in the path is encrypted separately.
 2. The methodof claim 1, further comprising storing in memory information regardingidentification and certification for the server, the plurality of accessfilters, and the user device.
 3. The method of claim 1, wherein theencrypted message is decrypted at the first access filter for accesschecking before transmitting to a second access filter.
 4. The method ofclaim 1, wherein encryption between a device pair forms a tunnel betweena device pair and wherein the tunnel is extended to a next device basedon the encryption between the device pair.
 5. The method of claim 1,wherein identifying the path ias based on current network routingconditions.
 6. The method of claim 1, wherein variable levels ofencryption are used in the path.
 7. The method of claim 6, furthercomprising selecting a level of encryption based on a trust levelbetween a device pair.
 8. An apparatus for controlling access to networkinformation, the apparatus comprising: memory for storing a local copyof one or more policies, the one or more policies limiting access to thenetwork information; a network interface for receiving a request from auser concerning access to information in a network; a processor forexecuting instructions stored in memory, wherein execution of theinstructions by the processor: determines that the user is authorized toaccess the requested network information based on at least the localcopy of the one or more policies, identifies a path through a pluralityof devices in the network, the plurality of devices including a serverhosting the requested network information, a plurality of accessfilters, and a user device associated with the user, and encrypts amessage containing the requested network information for transmissionbetween the server and a first access filter from the plurality ofaccess filters, wherein a plurality of transmissions of the messagebetween device pairs in the path is encrypted separately.
 9. Theapparatus of claim 8, further comprising storing in memory informationregarding identification and certification for the server, the pluralityof access filters, and the user device.
 10. The apparatus of claim 8,wherein the encrypted message is decrypted at the first access filterfor access checking before transmitting to a second access filter. 11.The apparatus of claim 8, wherein encryption between a device pair formsa tunnel between a device pair and wherein the tunnel is extended to anext device based on the encryption between the device pair.
 12. Theapparatus of claim 8, wherein identifying the path ias based on currentnetwork routing conditions.
 13. The apparatus of claim 8, whereinvariable levels of encryption are used in the path.
 14. The apparatus ofclaim 13, further comprising selecting a level of encryption based on atrust level between a device pair.
 15. A non-transitorycomputer-readable storage medium, having embodied thereon a programexecutable by a processor to perform a method for controlling access tonetwork information, the method comprising: storing a local copy of oneor more policies, the one or more policies limiting access to thenetwork information; receiving a request from a user concerning accessto information in a network; determining that the user is authorized toaccess the information based on at least the local copy of the one ormore policies; identifying a path through a plurality of devices in thenetwork, the plurality of devices including a server, a plurality ofaccess filters, and a user device associated with the user; andencrypting a message containing the requested information fortransmission between the server and a first access filter from theplurality of access filters, wherein each transmission between devicepairs in the path is encrypted separately.